Dual emulsion generation system and generation method

Abstract

The invention discloses a double emulsion generation system and a generation method, and belongs to the technical field of microfluidics. Comprising a liquid storage device, a pressure pumping device, a nested micro-fluidic chip and a double emulsion collecting tank, the liquid storage device is used for storing an internal phase fluid and an intermediate phase fluid, the pressure pumping device is communicated with the liquid storage device, and the liquid storage device is communicated with the nested micro-fluidic chip; a micro-channel is arranged in the nested micro-fluidic chip, and the micro-channel is of a micro-step structure. And the dual emulsion collecting tank is communicated with the nested micro-fluidic chip. The method does not involve micro-channel local surface modification, solves the problems of complex and unstable micro-channel local surface modification in the conventional double emulsion generation process, and greatly improves the production flux and production stability of the double emulsion.

Description

Technical Field

[0001] The invention relates to the field of microfluidic technology, and in particular to a double emulsion generation system and a generation method. Background Art

[0002] The statements in this section merely mention background art related to the present invention and do not necessarily constitute prior art.

[0003] Microfluidic chip technology can perform precise fluid control in microscale channels. It has been widely used in the fields of fluid mechanics, material synthesis, biomedicine, and pathogen detection, and has become an important tool for modern scientific research. In microfluidic technology, droplet microfluidics is an important branch. Emulsion droplets are a dispersed system containing two or more immiscible liquids. They have many applications in the food industry, drug preparation, and biochemical analysis. Single emulsions are usually unstable and have limited encapsulation capabilities. In contrast, double emulsions can encapsulate hydrophilic or hydrophobic compounds, thereby protecting the internal active substances from external influences and having better encapsulation stability.

[0004] Existing double emulsion generation technologies, such as T-shear method, flow focusing method, and coaxial flow method, all require surface modification of the internal microchannel. After the modification, one part of the microchannel is a hydrophobic surface and the other part is a hydrophilic surface. The surface modification is complicated and difficult to operate, and the surface coating is prone to failure, resulting in unstable double emulsion generation. The above factors limit the high-throughput production of double emulsions and their biomedical engineering applications.

[0005] Publication No. CN113826878B discloses a double emulsion generating device, which utilizes a mechanical structure to shear two immiscible fluids at high speed. Although the double emulsion generating steps are simplified, the generated double emulsion is uneven in size and has poor monodispersity. Publication No. CN117772020A discloses an assembled two-step step-type double emulsion batch preparation device, which involves the assembly and disassembly of different partitions, is complicated to operate, and has problems such as poor sealing and leakage, which affects the stability of double emulsion preparation. Summary of the invention

[0006] In order to address the shortcomings of the prior art, the present invention provides a double emulsion generation system and generation method. Aiming at the problem of complex and unstable local surface modification of microchannels in the conventional double emulsion generation process, two stepped emulsification microfluidic chips with micro-step structures are designed based on the Rayleigh-Plateau static instability of the fluid, and the two are nested in series to achieve graded fracture of the fluid, thereby greatly improving the production throughput and production stability of the double emulsion.

[0007] In a first aspect, the present invention provides a double emulsion generation system;

[0008] A double emulsion generating system, comprising:

[0009] A liquid storage device, the liquid storage device is used to store the inner phase fluid and the middle phase fluid;

[0010] a pressure pumping device, the pressure pumping device being in communication with the liquid storage device; and

[0011] A nested microfluidic chip, wherein the liquid storage device is connected to the nested microfluidic chip; a microchannel is arranged inside the nested microfluidic chip, and the microchannel has a micro-step structure;

[0012] A double emulsion collecting tank is communicated with the nested microfluidic chip.

[0013] In some embodiments, the nested microfluidic chip includes a first microfluidic chip and a second microfluidic chip, wherein the first microfluidic chip is disposed inside the second microfluidic chip and is in communication with the second microfluidic chip;

[0014] The microchannels are respectively arranged inside the first microfluidic chip and the second microfluidic chip. In some embodiments, the inner core thickness of the double emulsion is proportional to the height of the microchannel in the first microfluidic chip, and the middle phase spherical shell thickness of the double emulsion is proportional to the height of the microchannel in the second microfluidic chip.

[0015] In some embodiments, the liquid storage device comprises an inner phase liquid storage bottle and an intermediate phase liquid storage bottle, wherein the inner phase liquid storage bottle is used to store the inner phase fluid, and the intermediate phase liquid storage bottle is used to store the intermediate phase fluid;

[0016] The inner phase liquid storage bottle is connected to the first microfluidic chip, and the intermediate phase liquid storage bottle is connected to the second microfluidic chip.

[0017] In some embodiments, the pressure pumping device includes a pressure pump and a flow rate control device, the pressure pump is connected to the flow rate control device, and the flow rate control device is connected to the liquid storage device.

[0018] In some embodiments, the pressure pump is a vane pump, a positive displacement pump, or an electromagnetic pump.

[0019] In some embodiments, an external phase fluid is placed in the double emulsion collection tank.

[0020] In a second aspect, the present invention provides a method for producing a double emulsion;

[0021] A double emulsion generation method, based on the above double emulsion generation system, comprises:

[0022] The pressure pumping device delivers high-pressure gas to the liquid storage device, and delivers the internal phase gas and the external phase gas in the liquid storage device to the nested microfluidic chip;

[0023] Based on the micro-step structure of the nested microfluidic chip, under the action of Rayleigh-Plateau static instability, the inner phase fluid and the middle phase fluid form a double emulsion and are transported to the double emulsion collection tank.

[0024] In some embodiments, the pressure pumping device delivers the high-pressure gas to the liquid storage device, and delivers the internal phase gas and the external phase gas in the liquid storage device to the nested microfluidic chip specifically includes:

[0025] The pressure pumping device delivers high-pressure gas to the inner phase liquid storage bottle, and pumps the inner phase fluid into the first microfluidic chip;

[0026] The pressure pumping device delivers high-pressure gas to the intermediate phase storage bottle, and pumps the intermediate phase fluid into the second microfluidic chip.

[0027] In some embodiments, the micro-step structure based on the nested microfluidic chip, under the action of Rayleigh-Platte static instability, the inner phase fluid and the intermediate phase fluid form a double emulsion specifically including:

[0028] The inner phase fluid crosses the micro-step structure in the first microfluidic chip, and under the action of Rayleigh-Platte static instability, the inner phase fluid breaks into a single emulsion and is suspended in the middle phase fluid of the second microfluidic chip to form an middle phase fluid encapsulating the single emulsion;

[0029] The intermediate phase fluid encapsulating the single emulsion crosses the microstep structure in the second microfluidic chip. Under the action of Rayleigh-Plateau static instability, the intermediate phase fluid encapsulating the single emulsion breaks to form a double emulsion, which floats in the outer phase fluid.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The technical solution provided by the present invention is based on the Rayleigh-Platte static instability of the fluid, designs two stepped emulsification microfluidic chips with micro-step structures, and nests the two in series to achieve graded fracture of the fluid.

[0032] The internally nested microfluidic chip is used to induce the inner phase fluid to break the single emulsion. The single emulsion enters the external microfluidic chip driven by the intermediate phase fluid and breaks into a double emulsion at the micro-step structure.

[0033] The double emulsion generation system does not involve local surface modification of the microchannel, which solves the problem of complex and unstable local surface modification of the microchannel in the conventional double emulsion generation process, and greatly improves the production throughput and production stability of the double emulsion.

[0034] 2. The technical solution provided by the present invention clarifies the relationship between the structural dimensions of the double emulsion generation system and the size of the double emulsion, which facilitates production personnel to quantify and produce double emulsions on demand, thereby improving the speed and convenience of production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0036] Figure 1 A schematic diagram of the system architecture of a double emulsion production system provided by an embodiment of the present invention;

[0037] Figure 2 A schematic top view of a nested microfluidic chip provided in an embodiment of the present invention;

[0038] Figure 3 A physical schematic diagram of a microfluidic chip provided in an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of a process of generating a double emulsion in a "single channel" of a double emulsion generating system provided in an embodiment of the present invention;

[0040] Figure 5 A schematic diagram of a process of generating a double emulsion by a "multi-channel" double emulsion generating system provided by an embodiment of the present invention;

[0041] Figure 6 The microchannel height curves of the first microfluidic chip and the second microfluidic chip provided in the second embodiment of the present invention and the example diagram of the double emulsion generated under these conditions;

[0042] Figure 7 The microchannel height curves of the first microfluidic chip and the second microfluidic chip provided in Example 1 of the present invention and the example diagram of the double emulsion generated under these conditions;

[0043] Figure 8 The microchannel height curves of the first microfluidic chip and the second microfluidic chip provided in Example 2 of the present invention and the example diagram of the double emulsion generated under these conditions;

[0044] Fig. 9 The microchannel height curves of the first microfluidic chip and the second microfluidic chip provided in Example 3 of the present invention and the example diagram of the double emulsion generated under these conditions;

[0045] In the figure: 1. pressure pump; 2. flow rate control device; 3. gas pipeline; 4. inner phase liquid storage bottle; 5. intermediate phase liquid storage bottle; 6. inner phase fluid; 7. intermediate phase fluid; 8. fluid pipeline; 9. first microfluidic chip; 10. second microfluidic chip; 11. single emulsion; 12. double emulsion; 13. double emulsion collecting tank; 14. micro-step structure. DETAILED DESCRIPTION

[0046] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0047] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0048] Terminology explanation:

[0049] Plateau-Rayleigh Instability Theory: It is a theory that studies whether a cylindrical jet (Jet) is stable under external axial disturbances. That is, there is a critical wavelength λ for external disturbances of a cylindrical jet with a cross-sectional radius of r. Short-wave disturbances that are less than the critical wavelength will increase the surface energy of the system, and the disturbance will gradually decay and disappear over time, which is stable for the jet; while long-wave disturbances that are greater than the critical wavelength will reduce the surface energy of the system, and the disturbance will gradually increase until the jet breaks, which is unstable for the jet.

[0050] Principle of minimum surface energy: The reason why liquid droplets are round is due to the attraction of water molecules and surface tension. Since the surface tension is proportional to the surface area of ​​the liquid, the smaller the surface area, the less energy is required. Under the same mass, the surface area of ​​a spherical object is the smallest.

[0051] Embodiment 1

[0052] The generation of existing double emulsions 12 all relies on the surface modification of microchannels, but this step is complicated and difficult to operate, and the surface coating finally formed is easy to take effect, resulting in unstable double emulsion generation; therefore, the present invention provides a double emulsion generation system, which is based on the Rayleigh-Plateau instability of the fluid and uses a nested microfluidic chip with a microchannel with a micro-step structure 14 to achieve stable and efficient generation of double emulsions 12 without surface modification.

[0053] Next, combine Figure 1-Figure 5, a double emulsion generation system disclosed in this embodiment is described in detail. The double emulsion generation system includes a liquid storage device, a pressure pump 1 delivery device, a nested microfluidic chip and a double emulsion collection tank 13; the liquid storage device includes an inner phase liquid storage bottle 4 and an intermediate phase liquid storage bottle 5, the inner phase liquid storage bottle 4 is used to store the inner phase fluid 6, and the intermediate phase liquid storage bottle 5 is used to store the intermediate phase fluid 7; the nested microfluidic chip includes a first microfluidic chip 9 and a second microfluidic chip 10, the first microfluidic chip 9 and the second microfluidic chip 10 are cylindrical structures, and the first microfluidic chip 9 is vertically placed inside the second microfluidic chip 10 , and is connected to the second microfluidic chip 10, that is, the first microfluidic chip 9 is an inner microfluidic chip, and the second microfluidic chip 10 is an outer microfluidic chip; microchannels are respectively opened on the circumferential sides of the first microfluidic chip 9 and the second microfluidic chip 10; the pressure pump 1 delivery device includes a pressure pump 1 and a flow rate control device 2, the pressure pump 1 is used to provide high-pressure gas as a source of power for fluid movement, and the flow rate control device 2 is used to adjust the fluid flow rate; the double emulsion collection tank 13 is filled with external phase fluid, which is used to collect the generated double emulsion 12 droplets.

[0054] In this embodiment, the microchannel has a micro-step structure 14, that is, the microchannel includes a shallow channel and a micro-step structure 14 that are sequentially connected from the inside to the outside, and the cross-section of the microchannel is a rectangle and an isosceles trapezoid that are sequentially connected from the inside to the outside.

[0055] The interior of the first microfluidic chip 9 and the second microfluidic chip 10 is a storage area, and the storage area refers to the deep channel; the shallow channel of the first microfluidic chip 9 is connected to the deep channel of the second microfluidic chip 10 through the micro-step structure 14, and when the fluid crosses the micro-step structure 14, it breaks into micro droplets.

[0056] The pressure pump 1 is connected to the flow rate control device 2 through the gas pipeline 3, and the flow rate control device 2 is connected to the inner phase liquid storage bottle 4 and the intermediate phase liquid storage bottle 5 through the fluid pipeline 8 respectively. The inner phase liquid storage bottle 4 is connected to the inlet of the first microfluidic chip 9 through the fluid pipeline 8, and the intermediate phase liquid storage bottle 5 is connected to the inlet of the second microfluidic chip 10 through the fluid pipeline 8. The second microfluidic chip 10 is connected to the double emulsion collection tank 13 through the microchannel.

[0057] Furthermore, the gas pipeline 3 and the fluid pipeline 8 are made of glass, silicone or plastic, and the pressure pump 1 is a vane pump, a positive displacement pump or an electromagnetic pump. In this embodiment, the gas pipeline 3 and the fluid pipeline 8 are made of silicone, the pressure pump 1 is an electromagnetic pump, and the flow rate control device 2 is a flow controller.

[0058] The working mode of the double emulsion generation system described in this embodiment is as follows:

[0059] The pressure pump 1 compresses the external gas into high-pressure gas and delivers it to the flow rate regulating device, and then delivers it to the inner phase storage bottle 4 and the intermediate phase storage bottle 5 after the flow rate regulation. The high-pressure gas in the inner phase storage bottle 4 pumps the inner phase fluid 6 to the first microfluidic chip 9, and the high-pressure gas in the intermediate phase storage bottle 5 pumps the intermediate phase fluid 7 to the second layer of the microfluidic chip.

[0060] The first microfluidic chip 9 has a microchannel with a microstep structure 14. Therefore, when the inner phase fluid 6 crosses the microstep structure 14, under the action of Rayleigh-Platte static instability, the inner phase fluid 6 breaks into a single emulsion 11 and suspends in the intermediate phase fluid 7. Next, the intermediate phase fluid 7 wrapped in the single emulsion 11 enters the second microfluidic chip 10. The second microfluidic chip 10 also has a microchannel with a microstep structure 14. Under the action of Rayleigh-Platte static instability, the intermediate phase fluid 7 wrapped in the single emulsion 11 breaks to form a double emulsion 12, which floats in the outer phase fluid of the double emulsion collection tank 13. With the continuous driving of the high-pressure gas, the double emulsion 12 is continuously generated.

[0061] In this embodiment, part of the cross-section of the microchannel is rectangular, which can be equivalently transformed into a cylindrical shape. Therefore, the Rayleigh-Plato theory can be used to explore the process of fluid breaking into droplets in the microchannel. The flow of the fluid is not completely stable, but has certain disturbances. For example: the disturbance when the fluid enters the microfluidic chip, and the disturbance caused by avoiding relative motion with the microchannel. When the fluid enters the deep channel from the shallow channel, the axial disturbance is instantly amplified, resulting in an increase in the Laplace stress difference at the interface of the two-phase fluid, which causes the fluid to break into droplets.

[0062] In the first microfluidic chip 9 and the second microfluidic chip 10, the fluids that are necked and broken in the microchannels enter the corresponding deep channels respectively, and form a spherical single emulsion 11 and a spherical double emulsion 12 under the principle of minimum surface energy.

[0063] The gas pressure in the pressure pump 1 is 0-100 kPa, and the pressure adjustment range of the flow rate controller is 0-100 kPa, such as 20 kPa, 40 kPa, 60 kPa, 80 kPa or 100 kPa, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] Using the system described in this embodiment, the frequency of generating the double emulsion 12 is 1 Hz to 5000 Hz, such as 10 Hz, 500 Hz, 1000 Hz or 1500 Hz, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0065] Further, the microchannel height of the first microfluidic chip 9 and the second microfluidic chip 10 ranges from 1 μm to 1 mm, including 20 μm, 300 μm, 500 μm or 800 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0066] Based on the double emulsion generation system described in the present application, the inner core thickness of the double emulsion 12 is proportional to the microchannel height in the first microfluidic chip 9, and the intermediate phase spherical shell thickness of the double emulsion 12 is proportional to the microchannel height in the second microfluidic chip 10. Therefore, the user can adjust the size of the nested microfluidic chip according to the needs before generating the double emulsion 12, saving preparation time and improving efficiency.

[0067] Exemplarily, the inner core thickness of the double emulsion 12 is expressed as:

[0068] D 内部微滴直径 =h 1.6 ;

[0069] Wherein, h is the microchannel height of the first microfluidic chip 9.

[0070] The thickness of the mesophase shell of double emulsion 12 is expressed as:

[0071] A spherical shell thickness = D 外部微滴直径 -D 内部微滴直径 =H 1.6 -h 1.6 ;

[0072] Wherein, H is the microchannel height of the second microfluidic chip 10.

[0073] Embodiment 2

[0074] Combination Figure 5-Figure 9 Based on the double emulsion generation system described in Example 1, this embodiment discloses a double emulsion generation method, comprising the following steps:

[0075] S1, the pressure pump 1 delivery device delivers the high-pressure gas to the liquid storage device, and delivers the inner phase gas and the outer phase gas in the liquid storage device to the nested microfluidic chip.

[0076] Specifically, the pressure pump 1 compresses the external air and delivers it to the controller; the controller adjusts the gas pressure and delivers the compressed gas to the inner phase liquid storage bottle 4 and the intermediate phase liquid storage bottle 5 respectively through the gas hose; the high-pressure gas in the liquid storage bottles pumps the inner phase fluid 6 to the first microfluidic chip 9, and pumps the intermediate phase fluid 7 to the second microfluidic chip 10.

[0077] S2. Based on the micro-step structure 14 of the nested microfluidic chip, under the action of Rayleigh-Plateau static instability, the inner phase fluid 6 and the middle phase fluid 7 form a double emulsion 12 and are transported to the double emulsion collection tank 13.

[0078] Specifically include:

[0079] S201, the first microfluidic chip 9 has a microchannel with a microstep structure 14. Therefore, when the inner phase fluid 6 crosses the microstep structure 14, under the action of Rayleigh-Platte static instability, the inner phase fluid 6 breaks into a single emulsion 11 and is suspended in the intermediate phase fluid 7.

[0080] S202, the intermediate phase fluid 7 wrapping the single emulsion 11 enters the second microfluidic chip 10, and under the microchannel with a microstep structure 14 in the second microfluidic chip 10, under the action of Rayleigh-Platte static instability, the intermediate phase fluid 7 wrapping the single emulsion 11 breaks to form a double emulsion 12, and floats in the external phase fluid.

[0081] As the high-pressure gas continues to drive, the double emulsion 12 is continuously generated.

[0082] Next, the method described in this embodiment is described in detail with reference to specific examples:

[0083] Example 1

[0084] Combination Figure 6 This embodiment provides a double emulsion generation method, using the double emulsion generation system as described in Example 1, specifically comprising the following steps:

[0085] (1) The pressure pump 1 compresses the external air and delivers it to the controller; the controller adjusts the gas pressure and delivers the compressed gas to the inner phase liquid storage bottle 4 and the middle phase liquid storage bottle 5 through the gas hose.

[0086] (2) The high-pressure gas in the liquid storage bottle pumps the inner phase fluid 6 to the first microfluidic chip 9 (microchannel height is 20 μm), and pumps the intermediate phase fluid 7 to the second microfluidic chip 10 (microchannel height is 50 μm).

[0087] (3) The first microfluidic chip 9 has a micro-step structure 14. Therefore, when the inner phase fluid 6 crosses the micro-step structure 14, under the action of Rayleigh-Platte static instability, the inner phase fluid 6 breaks into a single emulsion 11 and is suspended in the intermediate phase fluid 7.

[0088] (4) The intermediate phase fluid 7 enveloping the single emulsion 11 enters the second microfluidic chip 10, which has a microstep structure 14. Under the action of Rayleigh-Plateau static instability, the intermediate phase fluid 7 enveloping the single emulsion 11 breaks, forming a double emulsion 12 that floats in the external phase fluid.

[0089] As the high-pressure gas continues to drive, the double emulsion 12 is continuously generated.

[0090] Example 2

[0091] This embodiment provides a double emulsion generation method, which is different from the embodiment 1 in that, while the microchannel height of the first microfluidic chip 9 remains unchanged, the microchannel height of the second microfluidic chip 10 is increased to 60 μm. Figure 7 As shown, under the continuous driving of high pressure gas, the first microfluidic chip 9 generates a single emulsion 11, and the second microfluidic chip 10 generates a double emulsion 12 (as shown in FIG. Figure 6 shown).

[0092] Combination Figure 6 and Figure 7 It can be found that when the microchannel height of the first microfluidic chip 9 remains unchanged, the greater the microchannel height of the second microfluidic chip 10 is, the thicker the intermediate phase spherical shell of the generated double emulsion 12 is, showing a positive correlation.

[0093] Example 3

[0094] This embodiment provides a double emulsion generation method, which is different from the embodiment 1 in that the height of the microchannel of the first microfluidic chip 9 is increased to 25 μm (eg, Figure 8 As shown). Under the continuous driving of the high-pressure gas, the first microfluidic chip 9 generates a single emulsion 11, and the second microfluidic chip 10 generates a double emulsion 12 (as shown). Figure 8 shown).

[0095] Combination Figure 6 and Figure 8 It can be found that when the microchannel height of the second microfluidic chip 10 remains unchanged, the larger the microchannel height of the first microfluidic chip 9 is, the larger the core of the generated double emulsion 12 is, showing a positive correlation.

[0096] Example 4

[0097] This embodiment provides a double emulsion generation method, which is different from the embodiment 1 in that the height of the microchannel of the first microfluidic chip 9 is reduced to 15 μm, and the height of the second microfluidic chip 10 is increased to 60 μm (such as Fig. 9As shown). Under the continuous driving of the high-pressure gas, the first microfluidic chip 9 generates a single emulsion 11, and the second microfluidic chip 10 generates a double emulsion 12 (as shown). Fig. 9 shown).

[0098] Combination Figure 6 and Fig. 9 It can be found that as the microchannel of the first microfluidic chip 9 decreases and the microchannel height of the second microfluidic chip 10 increases, the core of the generated double emulsion 12 becomes smaller and the intermediate phase spherical shell becomes thicker, showing a positive correlation.

[0099] The description of each embodiment in the above embodiments has different emphases. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0100] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A double emulsion generation system, characterized in that: include: A liquid storage device, the liquid storage device is used to store the inner phase fluid and the middle phase fluid; A pressure pumping device, the pressure pumping device is connected to the liquid storage device; as well as, A nested microfluidic chip, wherein the liquid storage device is connected to the nested microfluidic chip; a microchannel is arranged inside the nested microfluidic chip, and the microchannel has a micro-step structure; A double emulsion collecting tank is communicated with the nested microfluidic chip.

2. The double emulsion forming system according to claim 1, characterized in that: The nested microfluidic chip comprises a first microfluidic chip and a second microfluidic chip, wherein the first microfluidic chip is arranged inside the second microfluidic chip and is connected to the second microfluidic chip; The microchannels are respectively arranged inside the first microfluidic chip and the second microfluidic chip.

3. The double emulsion forming system according to claim 2, characterized in that: The inner core thickness of the double emulsion is proportional to the height of the microchannel in the first microfluidic chip, and the spherical shell thickness of the intermediate phase of the double emulsion is proportional to the height of the microchannel in the second microfluidic chip.

4. The double emulsion forming system according to claim 2, characterized in that: The liquid storage device comprises an inner phase liquid storage bottle and an intermediate phase liquid storage bottle, wherein the inner phase liquid storage bottle is used to store the inner phase fluid, and the intermediate phase liquid storage bottle is used to store the intermediate phase fluid; The inner phase liquid storage bottle is connected to the first microfluidic chip, and the intermediate phase liquid storage bottle is connected to the second microfluidic chip.

5. The double emulsion forming system according to claim 1, characterized in that: The pressure pumping device includes a pressure pump and a flow rate control device, the pressure pump is communicated with the flow rate control device, and the flow rate control device is communicated with the liquid storage device.

6. The double emulsion forming system according to claim 5, characterized in that: The pressure pump is a vane pump, a positive displacement pump or an electromagnetic pump.

7. The double emulsion forming system according to claim 1, characterized in that: The double emulsion collecting tank is provided with an external phase fluid.

8. A method for producing a double emulsion, characterized in that: The double emulsion generation system according to any one of claims 1 to 7 comprises: The pressure pumping device delivers high-pressure gas to the liquid storage device, and delivers the internal phase gas and the external phase gas in the liquid storage device to the nested microfluidic chip; Based on the micro-step structure of the nested microfluidic chip, under the action of Rayleigh-Plateau static instability, the inner phase fluid and the middle phase fluid form a double emulsion and are transported to the double emulsion collection tank.

9. The double emulsion forming method according to claim 8, wherein: The pressure pumping device delivers high-pressure gas to the liquid storage device, and delivers the internal phase gas and the external phase gas in the liquid storage device to the nested microfluidic chip specifically includes: The pressure pumping device delivers high-pressure gas to the inner phase liquid storage bottle, and pumps the inner phase fluid into the first microfluidic chip; The pressure pumping device delivers high-pressure gas to the intermediate phase storage bottle, and pumps the intermediate phase fluid into the second microfluidic chip.

10. The double emulsion forming method according to claim 8, characterized in that: The micro-step structure based on the nested microfluidic chip, under the action of Rayleigh-Plateau static instability, the inner phase fluid and the middle phase fluid form a double emulsion specifically including: The inner phase fluid crosses the micro-step structure in the first microfluidic chip, and under the action of Rayleigh-Platte static instability, the inner phase fluid breaks into a single emulsion and is suspended in the middle phase fluid of the second microfluidic chip to form an middle phase fluid encapsulating the single emulsion; The intermediate phase fluid encapsulating the single emulsion crosses the microstep structure in the second microfluidic chip. Under the action of Rayleigh-Plateau static instability, the intermediate phase fluid encapsulating the single emulsion breaks to form a double emulsion, which floats in the outer phase fluid.

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