A method for preparing single solid core water-in-oil droplets based on droplet splitting

Abstract

The application discloses a method for preparing single-solid-core solid water oil droplets based on droplet splitting, comprising the following steps: preparing a T-shaped micro-channel+Y-shaped micro-channel composite micro-fluidic chip, inserting a stainless steel capillary into the inlet and outlet of the composite micro-fluidic chip, and sealing the same by using AB glue; preparing a dispersed phase and a continuous phase; building a composite micro-fluidic platform, controlling the flow rates of the dispersed phase and the continuous phase by using a syringe pump, continuously generating double-solid-core solid water oil droplets at the T-shaped micro-channel, and splitting the double-solid-core solid water oil droplets into two single-solid-core solid water oil droplets at the Y-shaped micro-channel. The composite channel of the T-shaped micro-channel and the Y-shaped micro-channel is adopted to realize high-throughput preparation of single-solid-core solid water oil droplets, wherein the T-shaped micro-channel is used for preparing double-solid-core solid water oil droplets, and the Y-shaped micro-channel is used for splitting the double-solid-core solid water oil droplets, and two single-solid-core solid water oil droplets with uniform sizes are obtained after splitting.

Description

Technical Field

[0001] The present invention belongs to the field of microfluidic preparation of novel materials, and more specifically, relates to a method for preparing single solid-core solid-water-oil droplets based on droplet splitting. Background Art

[0002] Single-core, solid-water-oil droplets generated by microfluidic devices have a wide range of applications in biochemistry, drug delivery, functional materials, and inertial confinement fusion (ICF) experiments. In particular, in ICF implosion experiments, the most commonly used double-layer microspheres are precursors of single-core, solid-water-oil droplets. Because the solid core precursors used in implosion experiments are high-precision polystyrene (PS) hollow microspheres with extremely stringent requirements for sphericity, wall thickness uniformity, and surface smoothness, improving the utilization rate of these high-precision hollow microspheres is crucial in the preparation of single-core, solid-water-oil droplets.

[0003] Existing technologies are already able to produce single solid-core solid-water-oil droplets through co-flow, cross-flow and flow-focusing channels. However, in the process of preparing single solid-core solid-water-oil droplets using these methods, the generation of double solid-core solid-water-oil droplets is inevitable, which greatly reduces the utilization efficiency of high-precision hollow microspheres. At the same time, the preparation of single solid-core solid-water-oil droplets for thin liquid films requires a large continuous phase flow rate, which easily causes the solid-water-oil droplet system to become unstable, resulting in separation of the hollow microspheres from the liquid film, i.e., solid core decoating. The generation of double solid-core solid-water-oil droplets requires a smaller continuous phase flow rate. If the double solid-core solid-water-oil droplets can be evenly split, stable thin liquid film single solid-core solid-water-oil droplets can be obtained. Therefore, how to achieve controllable splitting of double solid-core solid-water-oil droplets to single solid-core solid-water-oil droplets is the key to improving the utilization rate of high-precision hollow microspheres and the efficiency of ICF target sphere preparation. Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these objects and other advantages of the present invention, a method for preparing single solid-core solid-water-oil droplets based on droplet splitting is provided, comprising the following steps:

[0006] Step 1: Prepare a T-shaped microchannel + Y-shaped microchannel composite microfluidic chip, insert stainless steel capillaries into the inlet and outlet of the composite microfluidic chip, and seal them with AB glue;

[0007] Step 2: Use a dropper to draw high-precision polystyrene (PS) hollow microspheres soaked in ultrapure water into a beaker. After absorbing all the water, add a polyvinyl alcohol (PVA) solution dropwise. After soaking for a period of time, use it as the dispersed phase. Then, prepare an oil phase solution mixed with dibutyl phthalate (DBP) and dioctyl sebacate (DOS) as the continuous phase.

[0008] Step 3: Build a composite microfluidic platform, use a syringe pump to control the flow rate of the dispersed phase and the continuous phase, continuously generate double solid-core solid-water-oil droplets in the T-shaped microchannel, and split them into two single solid-core solid-water-oil droplets in the Y-shaped microchannel.

[0009] Preferably, in step 1, the inlet of the composite microfluidic chip includes a dispersed phase channel inlet and a continuous phase channel inlet, the channel of the microfluidic chip is square, the channel side length is 1 mm, and the relationship between the channel side length and the diameter of the PS hollow microspheres is: PS hollow microsphere diameter + 100 μm ≤ channel side length ≤ 2 times the PS hollow microsphere diameter, the inner diameter of the stainless steel capillary ≥ PS hollow microsphere diameter + 100 μm, and the outer diameter of the stainless steel capillary < channel side length.

[0010] Preferably, in step 1, the T-shaped microchannel can be replaced by a cross channel or a Y-shaped microchannel, and the angle of the Y-shaped microchannel is 10° to 180°.

[0011] Preferably, in the step 1, when preparing the T-shaped microchannel + Y-shaped microchannel composite microfluidic chip, a serpentine microchannel is added between the T-shaped microchannel and the Y-shaped microchannel.

[0012] Preferably, in step 2, the diameter of the high-precision polystyrene (PS) hollow microspheres is 750±5 μm.

[0013] Preferably, in the step 2, the concentration of the polyvinyl alcohol (PVA) solution is 2 wt %, the molecular weight of the polyvinyl alcohol (PVA) is 13,000 to 23,000, and the degree of hydrolysis is 87 to 89%.

[0014] Preferably, in step 2, the volume ratio of dibutyl phthalate (DBP) to dioctyl sebacate (DOS) is 140-150:60-70.

[0015] Preferably, in the step three, the specific method of building the composite microfluidic platform is as follows: take a glass capillary, burn one end of the glass capillary with an alcohol burner so that its inner diameter is smaller than the diameter of the PS hollow microspheres to produce a limiting effect, insert the burned end into a PTFE hose, and absorb the PS hollow microspheres dispersed in the PVA solution into the glass capillary, and then use another section of PTFE hose to connect the unburned end of the glass capillary to the stainless steel capillary at the inlet of the dispersed phase channel, and then use another section of PTFE hose to connect the oil phase solution to the stainless steel capillary at the inlet of the continuous phase channel; then connect the unconnected ends of all PTFE hoses to different syringe pumps.

[0016] Preferably, in step 3, the ratio of the flow rate of the dispersed phase to the continuous phase is 0.89 to 1.6:1.

[0017] Preferably, in step three, when the composite microfluidic platform is built, the glass capillary can be replaced by a stainless steel capillary, and the alcohol burner burn limit can be replaced by a mechanical flattening limit. The outer diameter of the glass capillary is consistent with that of the stainless steel capillary, and the inner diameter is not more than that of the stainless steel capillary.

[0018] The present application at least includes the following advantages:

[0019] (1) The present application adopts a T-shaped microchannel to obtain double-solid-core solid water oil droplets, avoiding the problem of mixed double-solid-core solid water oil droplets in the process of directly generating single-solid-core solid water oil droplets, improving the use efficiency of high-precision solid cores, and ensuring the stability of subsequent droplets by generating a small continuous phase flow rate of double-solid-core solid water oil droplets, so that the collected single-solid-core solid water oil droplets are less likely to be de-coated.

[0020] (2) The present application can control the size of the generated double-solid-core solid water oil droplets within a certain range by adjusting the flow rate of each phase, thereby controlling the size of the single-solid-core solid water oil droplets after splitting at the Y-shaped microchannel, and the obtained single-solid-core solid water oil droplets are uniform in size and have good monodispersity; and a serpentine microchannel is added between the T-shaped microchannel and the Y-shaped microchannel to stabilize the droplet shape.

[0021] (3) The composite microfluidic chip of the present application can be reused, is simple to operate, and is easy to mass-produce.

[0022] Other advantages, objects, and features of the present application will be apparent from the following description, and will be understood by those skilled in the art through a study of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The present application is a composite microfluidic chip and a local high-speed camera photo;

[0024] Figure 2 The present application is a microfluidic chip schematic diagram;

[0025] Figure 3 The present application is a single-solid-core solid water oil droplet size distribution diagram in Example 1;

[0026] Figure 4 The present application is a single-solid-core solid water oil droplet size distribution diagram in Example 2;

[0027] Figure 5 The present application is a single-solid-core solid water oil droplet size distribution diagram in Example 3. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement the present application according to the description.

[0029] Example 1

[0030] A method for preparing single solid-core solid-water-oil droplets based on droplet splitting comprises the following steps:

[0031] Step 1: Prepare a composite microfluidic chip consisting of a T-shaped microchannel, a serpentine microchannel, and a Y-shaped microchannel using a CNC machine. The channel side length is 1 mm, and the Y-shaped microchannel angle is 30°. Stainless steel capillaries are inserted into the dispersed phase inlet, continuous phase inlet, and outlet of the composite microfluidic chip and sealed with AB glue.

[0032] Step 2: Prepare a 2% wt PVA aqueous solution (molecular weight 13,000, degree of hydrolysis 87%). Use a pipette to draw PS hollow microspheres (diameter 750 ± 5 μm) soaked in ultrapure water into a beaker. After absorbing all the water, add the PVA solution dropwise. After soaking for a period of time, use it as the dispersed phase. Then, use the oil phase solution mixed with 144 mL of DBP and 66 mL of DOS as the continuous phase.

[0033] Step 3: Take a glass capillary and burn one end of the glass capillary with an alcohol burner so that its inner diameter is smaller than the diameter of the PS hollow microspheres to produce a limiting effect. Insert the burned end into the PTFE hose and aspirate 50 PS hollow microspheres dispersed in the PVA solution into the glass capillary. Then use another section of PTFE hose to connect the unburned end of the glass capillary to the stainless steel capillary at the inlet of the dispersed phase channel. Then use another section of PTFE hose to connect the oil phase solution to the stainless steel capillary at the inlet of the continuous phase channel. Then connect the unconnected ends of all PTFE hoses to different syringe pumps. The dispersed phase flow rate and the continuous phase flow rate were controlled by an injection pump at 10 mL / h and 10 mL / h, respectively. Double solid-core solid-water-oil droplets were continuously generated in the T-shaped microchannel and split into two single solid-core solid-water-oil droplets in the Y-shaped microchannel. The size of the single solid-core solid-water-oil droplets obtained after splitting ranged from 1135 to 1365 μm, with an average size of 1249.9 μm and a coefficient of variation of 3.30%.

[0034] Example 2

[0035] A method for preparing single solid-core solid-water-oil droplets based on droplet splitting comprises the following steps:

[0036] Step 1: Prepare a composite microfluidic chip consisting of a T-shaped microchannel, a serpentine microchannel, and a Y-shaped microchannel using a CNC machine. The channel side length is 1 mm, and the Y-shaped microchannel angle is 60°. Stainless steel capillaries are inserted into the dispersed phase inlet, continuous phase inlet, and outlet of the composite microfluidic chip and sealed with AB glue.

[0037] Step 2: Prepare a 2% wt PVA aqueous solution (molecular weight 18,000, degree of hydrolysis 88%). Use a pipette to draw PS hollow microspheres (diameter 750 ± 5 μm) soaked in ultrapure water into a beaker. After absorbing all the water, add the PVA solution dropwise. After soaking for a period of time, use it as the dispersed phase. Then, use the oil phase solution mixed with 144 mL of DBP and 66 mL of DOS as the continuous phase.

[0038] Step 3: Take a glass capillary and burn one end of the glass capillary with an alcohol burner so that its inner diameter is smaller than the diameter of the PS hollow microspheres to produce a limiting effect. Insert the burned end into the PTFE hose and aspirate 50 PS hollow microspheres dispersed in the PVA solution into the glass capillary. Then use another section of PTFE hose to connect the unburned end of the glass capillary to the stainless steel capillary at the inlet of the dispersed phase channel. Then use another section of PTFE hose to connect the oil phase solution to the stainless steel capillary at the inlet of the continuous phase channel. Then connect the unconnected ends of all PTFE hoses to different syringe pumps. The dispersed phase flow rate was controlled at 20 mL / h and the continuous phase flow rate was 20 mL / h using a syringe pump. Double solid-core solid-water-oil droplets were continuously generated in the T-shaped microchannel and split into two single solid-core solid-water-oil droplets in the Y-shaped microchannel. The size of the single solid-core solid-water-oil droplets obtained after splitting was distributed in the range of 1130 to 1270 μm, with an average size of 1188.5 μm and a coefficient of variation of 2.97%.

[0039] Example 3

[0040] A method for preparing single solid-core solid-water-oil droplets based on droplet splitting comprises the following steps:

[0041] Step 1: Prepare a composite microfluidic chip consisting of a T-shaped microchannel, a serpentine microchannel, and a Y-shaped microchannel using a CNC machine. The channel side length is 1 mm, and the Y-shaped microchannel angle is 90°. Stainless steel capillaries are inserted into the dispersed phase inlet, continuous phase inlet, and outlet of the composite microfluidic chip and sealed with AB glue.

[0042] Step 2: Prepare a 2% wt PVA aqueous solution (molecular weight 23,000, degree of hydrolysis 89%). Use a pipette to draw PS hollow microspheres (diameter 750 ± 5 μm) soaked in ultrapure water into a beaker. After absorbing all the water, add the PVA solution dropwise. After soaking for a period of time, use it as the dispersed phase. Then, use the oil phase solution mixed with 144 mL of DBP and 66 mL of DOS as the continuous phase.

[0043] Step 3: Take a glass capillary and burn one end of the glass capillary with an alcohol burner so that its inner diameter is smaller than the diameter of the PS hollow microspheres to produce a limiting effect. Insert the burned end into the PTFE hose and aspirate 50 PS hollow microspheres dispersed in the PVA solution into the glass capillary. Then use another section of PTFE hose to connect the unburned end of the glass capillary to the stainless steel capillary at the inlet of the dispersed phase channel. Then use another section of PTFE hose to connect the oil phase solution to the stainless steel capillary at the inlet of the continuous phase channel. Then connect the unconnected ends of all PTFE hoses to different syringe pumps. The dispersed phase flow rate was controlled at 30 mL / h and the continuous phase flow rate was 30 mL / h using a syringe pump. Double solid-core solid-water-oil droplets were continuously generated in the T-type microchannel and split into two single solid-core solid-water-oil droplets in the Y-type microchannel. The size of the single solid-core solid-water-oil droplets obtained after splitting was distributed in the range of 1080 to 1240 μm, with an average size of 1149.7 μm and a coefficient of variation of 3.49%.

[0044] Comparative Example 1

[0045] A method for preparing monodisperse solid-water-oil composite emulsion particles comprises the following steps:

[0046] Step 1: Prepare PS hollow microspheres with a diameter of 750±5 μm, i.e., solid core, using a coaxial emulsion generator;

[0047] Step 2: Prepare a cross-flow focusing microfluidic device with a vertical main channel and a horizontal side channel having a diameter of 1 mm by using a casting method;

[0048] Step 3: Prepare a PVA solution with a molecular weight of 13,000, a degree of hydrolysis of 87%, and a mass concentration of 2% according to the density matching range requirements; mix 144 mL of DBP and 66 mL of DOS as the oil phase solution;

[0049] Step 4: Use the aqueous PVA solution to absorb 50 PS hollow microspheres containing internal phase water into the capillary; the capillary is tightly connected to the vertical main channel of the cross-flow focusing microfluidic device, and the oil phase solution is tightly connected to the horizontal side channels on both sides of the cross-flow focusing microfluidic device using hoses;

[0050] Step 5. Use a syringe pump to control the flow rate of the vertical main channel and the horizontal side channels on both sides, adjust the volume flow rate of the vertical main channel to 20 mL / h, and the volume flow rate of the horizontal side channel to 20 mL / h; form a dispersed phase in the vertical main channel, and form a continuous phase in the horizontal side channels on both sides; when the dispersed phase and the continuous phase meet at the cross of the cross flow focusing microfluidic device, the dispersed phase is sheared by the continuous phase to form solid-water-oil composite emulsion particles; after the solid-water-oil composite emulsion particles are formed, they are transported through the straight pipe at the lower end of the cross flow focusing microfluidic device to obtain solid-water-oil composite emulsion particles, that is, single solid-core solid-water-oil droplets.

[0051] The geometric size test results show that the size of the obtained single solid-core solid-water-oil droplets is distributed between 840 and 885 μm, with a coefficient of variation of 5%.

[0052] Comparative Example 2

[0053] A method for preparing monodisperse solid-water-oil composite emulsion particles comprises the following steps:

[0054] Step 1: Prepare PS hollow microspheres with a diameter of 800±5 μm, i.e., solid core, using a coaxial emulsion generator;

[0055] Step 2: Prepare a cross-flow focusing microfluidic device with a vertical main channel and a horizontal side channel having a diameter of 1 mm by using a casting method;

[0056] Step 3: Prepare a PVA solution with a molecular weight of 13,000, a degree of hydrolysis of 87%, and a mass concentration of 2% according to the density matching range requirements; mix 140 mL of DBP and 70 mL of DOS as the oil phase solution;

[0057] Step 4: Using an aqueous PVA solution, 50 polystyrene hollow microspheres containing internal water were drawn into a capillary tube. The capillary tube was then tightly connected to the vertical main channel of a cross-flow focusing microfluidic device. At the same time, a flexible tube was used to tightly connect the oil phase solution to the horizontal side channels on both sides of the cross-flow focusing microfluidic device.

[0058] Step 5. Use a syringe pump to control the flow rate of the vertical main channel and the horizontal side channels on both sides, adjust the volume flow rate of the vertical main channel to 40mL / h, and the volume flow rate of the horizontal side channel to 40mL / h; form a dispersed phase in the vertical main channel, and form a continuous phase in the horizontal side channels on both sides; when the dispersed phase and the continuous phase meet at the cross of the cross flow focusing microfluidic device, the dispersed phase is sheared by the continuous phase to form solid-water-oil composite emulsion particles; after the solid-water-oil composite emulsion particles are formed, they are transported through the straight pipe at the lower end of the cross flow focusing microfluidic device to obtain solid-water-oil composite emulsion particles, that is, single solid-core solid-water-oil droplets.

[0059] The geometric size test results show that the size of the obtained single solid core solid water oil droplets is distributed between 880 and 925 μm, with a coefficient of variation of 7%.

[0060] Comparative Example 3:

[0061] A method for preparing monodisperse solid-water-oil composite emulsion particles comprises the following steps:

[0062] Step 1: Prepare PS hollow microspheres with a diameter of 850±5 μm, i.e., solid core, using a coaxial emulsion generator;

[0063] Step 2: Prepare a cross-flow focusing microfluidic device with a vertical main channel and a horizontal side channel having a diameter of 1 mm by using a casting method;

[0064] Step 3: Prepare a PVA solution with a molecular weight of 15,000, a degree of hydrolysis of 90%, and a mass concentration of 3% according to the density matching range requirements; mix 140 mL of DBP, 70 mL of DOS, and 70 mL of dioctyl phthalate (DOP) as the oil phase solution;

[0065] Step 4: Using an aqueous PVA solution, 50 polystyrene hollow microspheres containing internal water were drawn into a capillary tube. The capillary tube was tightly connected to the vertical main channel of the cross-flow focusing microfluidic device. At the same time, a flexible tube was used to tightly connect the oil phase solution to the horizontal side channels on both sides of the cross-flow focusing microfluidic device. The inner diameter of the capillary tube was consistent with the inner diameter of the vertical main channel of the cross-flow focusing microfluidic device.

[0066] Step 5. Use a syringe pump to control the flow rate of the vertical main channel and the horizontal side channels on both sides, adjust the volume flow rate of the vertical main channel to 30 mL / h, and the volume flow rate of the horizontal side channel to 30 mL / h; form a dispersed phase in the vertical main channel, and form a continuous phase in the horizontal side channels on both sides; when the dispersed phase and the continuous phase meet at the cross of the cross flow focusing microfluidic device, the dispersed phase is sheared by the continuous phase to form solid-water-oil composite emulsion particles; after the solid-water-oil composite emulsion particles are formed, they are transported through the straight pipe at the lower end of the cross flow focusing microfluidic device to obtain solid-water-oil composite emulsion particles, that is, single solid-core solid-water-oil droplets.

[0067] The geometric size test results show that the size of the obtained single solid-core solid-water-oil droplets is distributed in the range of 945 to 995 μm, with a coefficient of variation of 8%.

[0068] Comparative Examples 1-3 all used a cross-shear method to produce single-core solid-water-oil composite emulsions, and their coefficients of variation were relatively high, at 5%, 7%, and 8%, respectively, indicating that Comparative Examples 1-3 could not stably produce solid-water-oil droplets. The present invention, on the other hand, used a T-shaped channel to stably generate dual-core solid-water-oil droplets, and then used a Y-shaped channel to split them to prepare single-core solid-water-oil droplets. The coefficients of variation in the three examples were 3.30%, 2.97%, and 3.49%, respectively, all superior to the comparative examples, and could avoid the problem of generating dual-core droplets when directly generating single-core solid-water-oil droplets.

[0069] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing single solid-core solid-water-oil droplets based on droplet fission, characterized in that: The following steps are involved: Step 1: Prepare a droplet-forming microchannel + Y-shaped microchannel composite microfluidic chip, insert a stainless steel capillary into the inlet and outlet of the composite microfluidic chip, and seal them with AB glue. The angle of the Y-shaped microchannel is 30° to 90°; Step 2: Use a dropper to draw high-precision polystyrene hollow microspheres soaked in ultrapure water into a beaker, drain the water and then drip into the polyvinyl alcohol solution. After soaking for a period of time, use it as the dispersed phase. Then, prepare an oil phase solution mixed with dibutyl phthalate and dioctyl sebacate as the continuous phase. Step 3: Build a composite microfluidic platform and use a syringe pump to control the flow rate of the dispersed phase and the continuous phase to continuously generate double solid-core solid-water-oil droplets in the T-shaped microchannel and split them into two single solid-core solid-water-oil droplets in the Y-shaped microchannel; In the step 1, the inlet of the composite microfluidic chip includes a dispersed phase channel inlet and a continuous phase channel inlet. The cross-section of the channel of the microfluidic chip is a square cross-section. The side length of the square cross-section is 1 mm. The relationship between the side length of the square cross-section and the diameter of the PS hollow microsphere is: PS hollow microsphere diameter + 100 μm ≤ square cross-section ≤ 2 times the PS hollow microsphere diameter, the inner diameter of the stainless steel capillary ≥ PS hollow microsphere diameter + 100 μm, and the outer diameter of the stainless steel capillary < square cross-section.

2. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In the step 1, the droplet-forming microchannel is a T-shaped microchannel, a cross-shaped microchannel, or a Y-shaped microchannel.

3. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In the step 1, when preparing the droplet-forming microchannel+Y-shaped microchannel composite microfluidic chip, a serpentine microchannel is added between the droplet-forming microchannel and the Y-shaped microchannel.

4. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In the step 2, the diameter of the high-precision polystyrene hollow microspheres is 750±5 μm.

5. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In the step 2, the concentration of the polyvinyl alcohol solution is 2 wt %, the molecular weight of the polyvinyl alcohol is 13,000-23,000, and the degree of hydrolysis is 87-89%.

6. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In the step 2, the volume ratio of dibutyl phthalate to dioctyl sebacate is 140-150:60-70.

7. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In step three, the specific method for constructing the composite microfluidic platform is as follows: taking a glass capillary, burning one end of the glass capillary with an alcohol burner so that its inner diameter is smaller than the diameter of the PS hollow microspheres to produce a limiting effect, inserting the burned end into a PTFE hose, and sucking the PS hollow microspheres dispersed in the PVA solution into the glass capillary, then using another section of PTFE hose to connect the unburned end of the glass capillary to the stainless steel capillary at the inlet of the dispersed phase channel, and then using another section of PTFE hose to connect the oil phase solution to the stainless steel capillary at the inlet of the continuous phase channel; and then connecting the unconnected ends of all PTFE hoses to different syringe pumps.

8. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 1, characterized in that: In the step 3, the ratio of the dispersed phase to the continuous phase flow rate is 0.89-1.6:

1.

9. The method for preparing single solid-core solid-water-oil droplets based on droplet fission according to claim 7, characterized in that: In step three, when building the composite microfluidic platform, the glass capillary can be replaced by a stainless steel capillary, the alcohol burner burning limit can be replaced by a mechanical flattening limit, the outer diameter of the glass capillary is consistent with that of the stainless steel capillary, and the inner diameter does not exceed that of the stainless steel capillary.

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