Method for in situ generation of microdroplets and system therefor

Abstract

The application provides a method for generating microdroplets in situ, wherein the microdroplets are generated in situ and captured in situ; the microdroplets are generated by a microdroplet generation device, the microdroplet generation device comprises one or more microdroplet generation and capture zones 101, the microdroplet generation and capture zones 101 are arranged in a flow channel 102, and the flow channel 102 is provided with a fluid inlet 103 and a fluid outlet 104. In the application, the size of the microdroplets formed can be controlled by controlling the size of the microdroplet generation and capture zones, and the flexibility and controllability are high; in the application, high-throughput droplet generation and in-situ capture can be realized by increasing the number of microdroplet generation and capture units.

Description

Technical Field

[0001] This invention relates to the field of microfluidics, and in particular to a method and system for in-situ generation of microdroplets. Background Technology

[0002] Droplet microfluidics is an important branch of microfluidic chip technology. This technology achieves precise formation and control of tiny droplets by manipulating fluids in micrometer-scale channels. The basic principles of droplet microfluidics encompass the microscale effects of fluids, the role of surface tension, and fluid flow control. In microfluidic channels, liquids are broken down into tiny droplets, and the formation of these droplets is closely related to the structure of the microchannel and the properties of the fluid.

[0003] Droplet microfluidics not only possesses the inherent advantages of traditional microfluidics, such as small size, low sample volume, high speed, and high throughput, but also features uniform droplet size and internal stability. These characteristics make droplet microfluidics a promising field for applications. For example, in biology, droplet microfluidics can be used for highly integrated processes in cell culture, experimental handling, imaging, and detection. In medicine, it is widely used in IVD detection, controlled drug release, antibody screening, and biomarker detection. Furthermore, droplet microfluidics can also be used in particulate material synthesis, droplet barcode sequencing, catalyst preparation, and tissue engineering.

[0004] Droplet microfluidics typically involves operations such as droplet generation, splitting / fusion, capture, reaction, detection, and sorting. Droplet generation can be categorized into passive and active droplet generation methods based on the applied force. Passive droplet generation uses channel geometry (such as T-type / Y-type structures, flow focusing structures, coaxial flow focusing structures, and stepped structures) to separate a discrete phase fluid into uniformly sized microdroplets within a continuous phase fluid. This method offers advantages such as uniform size, good monodispersity, and effective avoidance of external interference; however, it requires high precision in the channel geometry. Active droplet generation utilizes external force fields such as batteries, magnetic fields, and acoustic fields to form droplets. Compared to passive methods, active droplet generation offers better droplet control, but its generation devices are more complex. For droplet capture, currently common methods primarily employ specialized geometric "trap" structures, which are complex and difficult to fabricate.

[0005] Typically, droplet generation and droplet capture require two separate functional structures. When developing an integrated droplet system, droplet generation, droplet capture, and other necessary functional units are integrated together. On the one hand, this integrated structure is generally quite complex and difficult to fabricate. On the other hand, at the initial startup of such a system, the size and shape of the droplets are usually not stable due to factors such as equipment stability and changes in internal chip flow resistance, requiring a period of time before droplets of controlled size can be stably formed. Summary of the Invention

[0006] To address the aforementioned problems, the present invention provides a method for in-situ generation of microdroplets, wherein the microdroplets are generated and captured in situ; the microdroplets are generated by a microdroplet generation device, the microdroplet generation device including one or more microdroplet generation and capture zones 101, the droplet generation and capture zones 101 being disposed in a flow channel 102, the flow channel 102 being provided with a fluid inlet 103 and a fluid outlet 104;

[0007] When water-in-oil microdroplets are generated, the surface of the fluid flow area in the flow channel 102 is a hydrophobic surface, and the contact angle between the hydrophobic surface and water is not less than 90°. The surface of the droplet generation and capture area 101 in the flow channel 102 is a hydrophilic surface, and the contact angle between the hydrophilic surface and water is at least 40° smaller than the contact angle between the surrounding hydrophobic surface and water.

[0008] When generating microdroplets, an aqueous phase fluid is driven to fill the microdroplet generation and capture zone 101 and the flow channel 102 through the fluid inlet 103. Then, the injection of the aqueous phase fluid is stopped, and an oil phase fluid is driven to be injected into the flow channel 102 through the fluid inlet 103. During the process of the oil phase fluid covering the flow channel 102, the droplet generation and capture zone 101 is hydrophilic and will hold the aqueous phase fluid in the droplet generation and capture zone 101. The aqueous phase fluid not in the droplet generation and capture zone 101 will be pushed towards the fluid outlet 104 along with the flow of the oil phase fluid. In this process, through the pulling / pushing of the aqueous phase fluid, the aqueous phase fluid can be sheared into microdroplets of a certain size and finally fixed at the position of the droplet generation and capture zone 101.

[0009] Alternatively, when generating oil-in-water microdroplets, the surface of the fluid flow area in the flow channel 102 is a hydrophilic surface, and the contact angle between the hydrophilic surface and water is no greater than 90°. The surface of the droplet generation and capture area 101 disposed in the flow channel 102 is a hydrophobic surface, and the contact angle between the hydrophobic surface and water is at least 40° larger than the contact angle between the hydrophilic surface and water around it.

[0010] When generating microdroplets, the driving oil phase fluid fills the microdroplet generation and capture zone 101 and the flow channel 102 through the fluid inlet 103. Then, the injection of the oil phase fluid stops, and the driving water phase fluid is injected into the flow channel 102 through the fluid inlet 103. During the process of the water phase fluid covering the flow channel 102, the droplet generation and capture zone 101 is hydrophobic and will hold the oil phase fluid in the droplet generation and capture zone 101. The oil phase fluid not in the droplet generation and capture zone 101 will be pushed towards the fluid outlet 104 along with the flow of the water phase fluid. In this process, through the pulling / pushing of the oil phase fluid, the oil phase fluid can be sheared into microdroplets of a certain size and finally fixed at the position of the droplet generation and capture zone 101.

[0011] In one embodiment, when generating water-in-oil microdroplets, the contact angle between the hydrophobic surface and water is not less than 100°, and the contact angle between the hydrophilic surface and water is not greater than 60°.

[0012] In one embodiment, when generating water-in-oil microdroplets, the entire flow channel 102 is made of a hydrophobic material, with only the droplet generation and capture region 101 undergoing localized hydrophilic treatment.

[0013] In one embodiment, the flow channel 102 is prepared using PDMS.

[0014] In one embodiment, the droplet generation and capture region 101 is locally hydrophilicized by plasma treatment, chemical reagent modification, or chemical liquid phase deposition.

[0015] In one embodiment, the droplet generation and capture zone 101 is locally hydrophilic by depositing polyN-isopropylacrylamide on the surface of the capture zone using a chemical liquid phase deposition method.

[0016] In one embodiment, the droplet generation and capture region 101 is circular or polygonal.

[0017] In one embodiment, the size of the generated microdroplets is changed by altering the size of the droplet generation and capture region 101, and / or, when generating water-in-oil microdroplets, the size of the generated microdroplets is changed by altering the flow rate of the oil phase fluid, and when generating oil-in-water microdroplets, the size of the generated microdroplets is changed by altering the flow rate of the aqueous phase fluid.

[0018] In one embodiment, a system for in-situ generation of microdroplets used in the above method is provided.

[0019] In one embodiment, the system includes a droplet generation and capture integrated chip, which includes a microdroplet generation and capture unit 1, a first inlet 2, a second inlet 3, an outlet 4, a first fluid inlet channel 5 connected to the first inlet 2, a second fluid inlet channel 6 connected to the second inlet 3, an inlet channel 7, a droplet channel 8, and an outlet channel 9. The microdroplet generation and capture unit 1 is disposed in the droplet channel 8 and includes at least one droplet generation and capture region 101. The first inlet 2 and the second inlet 3 are used to introduce aqueous fluid and oil fluid, respectively. The first fluid enters the inlet channel 7 through the first fluid inlet channel 5, and the second fluid enters the inlet channel 7 through the second fluid inlet channel 6.

[0020] In this invention, microdroplets are generated and captured in situ, integrating microdroplet generation and capture into a single structure. This structure is simple, highly integrated, and facilitates control of the microdroplet generation process and detection. Furthermore, this invention achieves flexible and controllable microdroplet generation and in-situ capture through localized hydrophilic / hydrophobic treatment.

[0021] In the method of the present invention, after the droplet is generated and captured, the continued flow of the oil phase as a continuous phase not only does not push the generated droplet away from the droplet generation and capture area, but also drives the liquid flow inside the aqueous droplet, that is, the internal circulation phenomenon of the aqueous droplet, which can further improve the mass transfer efficiency inside the droplet.

[0022] In the method of this invention, the stability of the pump valves and changes in flow resistance at the initial stage of system startup have little impact on droplet generation, resulting in high system stability and reliable generation of microdroplets, thus avoiding instability during microdroplet production. In this invention, the size of the formed microdroplets can be controlled by adjusting the size of the droplet generation and capture zone, offering high flexibility and controllability. Furthermore, by increasing the number of droplet generation and capture units, high-throughput droplet generation and in-situ capture can be achieved. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of an embodiment of the microdroplet generation and capture region of the present invention;

[0025] Figure 2These are images illustrating the actual microdroplet generation and capture process in the microdroplet generation and capture area of ​​this invention;

[0026] Figure 3 It is a simulation result diagram showing the fluid flow state of the trapped droplets under continuous flow of a continuous phase;

[0027] Figure 4 This is a schematic diagram and experimental results of an embodiment of the droplet generation and capture integrated chip of the present invention;

[0028] Figure 5 This invention demonstrates the capture effect of droplet generation and capture zones of different sizes (from left to right, the diameters of the droplet generation and capture zones are 0.5 mm, 0.4 mm, and 0.3 mm, respectively).

[0029] Figure 6 This invention presents a graph showing the diameter data of droplets generated and captured by droplet generation and capture zones of different sizes at different flow rates. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions in this application, the present invention will be further described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0031] Example 1: Method for in-situ generation of microdroplets according to the present invention

[0032] This invention provides a method for in-situ generation and in-situ capture of microdroplets, such as... Figure 1 As shown, the microdroplet generation device of the present invention includes a microdroplet generation and capture area 101, a flow channel 102, an inlet 103, and an outlet 104. The droplet generation and capture area 101 can be of various shapes such as circular or polygonal, with external dimensions (such as length, width, and diameter) of 0.1 mm or more. The flow channel 102 has a channel width of 0.1 mm or more and a channel depth of 0.05 mm or more.

[0033] For capturing water-in-oil (W / O) microdroplets, the entire flow channel is made of a hydrophobic material (such as PDMS) (the contact angle of the hydrophobic material is greater than 90°, preferably greater than 100°), and only the droplet generation and capture region 101 is locally hydrophilic (e.g., by plasma treatment, chemical reagent modification or chemical liquid phase deposition, the contact angle of the hydrophilic region must be less than 60°), and the contact angles of the hydrophobic material and the hydrophilic material must have a difference of 40° or more.

[0034] During operation, the aqueous phase fluid first fills the droplet generation and capture zone 101 and the flow channel 102 through inlet 103 under the action of the fluid-driven pump. Then, the injection of the aqueous phase fluid stops, and the oil phase fluid is driven to be injected into the flow channel 102 through inlet 103. As the oil phase fluid covers the flow channel 102, the droplet generation and capture zone 101, due to its hydrophilic coating, holds back the aqueous phase fluid near the hydrophilic coating, while the aqueous phase fluid not in the droplet generation and capture zone 101 is pushed towards the outlet 104 along with the flow of the oil phase. During this process, through the pulling / pushing action of the aqueous phase fluid, it can be sheared into droplets of a certain size, which are ultimately fixed at the location of the droplet generation and capture zone 101 (see [link to experimental results]). Figure 2 After the droplets are generated and captured, the continued flow of the oil phase, as the continuous phase, not only does not push the generated droplets away from the droplet generation and capture zone 101, but also drives the liquid flow inside the aqueous phase droplets (see...). Figure 3 Simulation results show that the internal circulation phenomenon of aqueous droplets can further improve the mass transfer efficiency within the droplets.

[0035] For the generation and capture of oil-in-water (O / W) microdroplets, the droplet generation and capture region 101 is hydrophobic, while other locations are hydrophilic. The specific generation and capture mechanism of oil-in-water microdroplets is similar to that of oil-in-water, and will not be elaborated here.

[0036] Example 2: The system for in-situ generation of microdroplets according to the present invention

[0037] The system for in-situ generation of microdroplets of the present invention includes an integrated chip for droplet generation and capture, in such a way as... Figure 4 In one embodiment shown, the droplet generation and capture integrated chip includes a microdroplet generation and capture unit 1, a first inlet 2, a second inlet 3, an outlet 4, a first fluid inlet channel 5 connected to the first inlet 2, a second fluid inlet channel 6 connected to the second inlet 2, an inlet channel 7, a droplet channel 8, and an outlet channel 9. The microdroplet generation and capture unit 1 includes at least one droplet generation and capture region 101, and the microdroplet generation and capture unit 1 is disposed in the droplet channel 8. The first inlet 2 and the second inlet 3 are used to introduce aqueous and oil phase fluids, respectively.

[0038] For the generation and capture of water-in-oil microdroplets, the integrated chip for droplet generation and capture is fabricated using a hydrophobic material (such as PDMS), with only localized hydrophilic treatment performed on the droplet generation and capture region 101 of the microdroplet generation and capture unit 1 (e.g., using plasma treatment + chemical reagent modification or chemical liquid phase deposition). During operation, the aqueous phase fluid first flows into the chip through the first inlet 2 under the action of a fluid-driven pump, and sequentially passes through and fills the first fluid inlet channel 5, the inlet channel 7, the droplet channel 8, and the droplet generation and capture region 101, before flowing out of the chip through the outlet channel 9 and the outlet 4. Afterward, the aqueous phase injection stops, while the oil phase fluid flows into the microfluidic chip through the second inlet 3, and sequentially fills the second fluid inlet channel 6, the inlet channel 7, and the droplet channel 8, before flowing out of the chip through the outlet channel 9 and the outlet 4. During the process of the oil phase fluid covering the droplet channel 8, the droplet generation and capture zone 101, due to its hydrophilic coating, will hold back the aqueous phase fluid near the hydrophilic coating, while the aqueous phase fluid not in the droplet generation and capture zone 101 will be pushed towards the outlet 4 along with the flow of the oil phase. In this process, the pulling / pushing of the aqueous phase fluid near the droplet generation and capture zone 101 will shear the aqueous phase fluid into micro-droplets of a certain size. After being generated, the micro-droplets will be fixed at the location of the droplet generation and capture zone 101, thus realizing the generation and in-situ capture of micro-droplets.

[0039] Example 3: Generation of Microdroplets of the Present Invention

[0040] like Figure 4 In the illustrated embodiment, the droplet generation and capture integrated chip has eight identical circular droplet generation and capture regions 101 with a diameter of 0.3 mm. The channel width of the flow channel 102 is 1 mm, and the overall depth of the chip is 0.1 mm. The chip as a whole is made of PDMS material with a contact angle of approximately 110°, and a hydrophilic coating of poly(N-isopropylacrylamide) (PNIPAAm) with a contact angle of approximately 50° is formed on the surface of the droplet generation and capture region using a chemical liquid phase deposition method. The specific operation is as follows:

[0041] (1) The aqueous fluid is injected into the chip from the first inlet 2 at a flow rate of 0.3 μL / min, and passes through and fills the first fluid inlet channel 5, the inlet channel 7, the droplet channel 8, and the droplet generation and capture area 101 in sequence, and then flows out of the chip through the outlet channel 9 and the outlet 4.

[0042] (2) Set the flow rate of the aqueous phase fluid to 0 μL / min.

[0043] (3) The oil phase fluid is injected into the chip from the second inlet 3 at a flow rate of 0.3 μL / min, and sequentially fills the second fluid inlet channel 6, the inlet channel 7, and the droplet channel 8, before flowing out of the chip through the outlet channel 9 and the outlet 4. During the process of the oil phase fluid covering the droplet channel 8, droplets are sequentially generated in the eight circular droplet generation and capture areas 101, and the droplets are fixed on the droplet generation and capture areas 101. Specific experimental results can be found in […]. Figure 4 The generated droplets are very uniform in size.

[0044] Example 4: Experiment on factors affecting the generation of microdroplets in this invention

[0045] like Figure 5 , 6 In the illustrated embodiment, the droplet generation and capture integrated chip has six circular droplet generation and capture regions 101 with diameters of 0.5 mm, 0.5 mm, 0.4 mm, 0.4 mm, 0.3 mm, and 0.3 mm, respectively. The channel width of the flow channel 102 is 1.3 mm, and the overall chip depth is 0.1 mm. The chip as a whole uses PDMS material with a contact angle of approximately 110°, and a hydrophilic coating of poly(N-isopropylacrylamide) (PNIPAAm) with a contact angle of approximately 50° is formed on the surface of the droplet generation and capture region using a chemical liquid phase deposition method. The specific operation is as follows:

[0046] (1) The aqueous fluid is injected into the chip from the first inlet 2 at a flow rate of 0.3 μL / min, and passes through and fills the first fluid inlet channel 5, the inlet channel 7, the droplet channel 8, and the droplet generation and capture area 101 in sequence, and then flows out of the chip through the outlet channel 9 and the outlet 4.

[0047] (2) Set the flow rate of the aqueous phase fluid to 0 μL / min.

[0048] (3) The oil phase fluid is injected into the chip from the second inlet 3 at a flow rate of 0.2–0.8 μL / min, sequentially filling the second fluid inlet channel 6, the inlet channel 7, and the droplet channel 8, and then flowing out of the chip through the outlet channel 9 and the outlet 4. During the process of the oil phase fluid covering the droplet channel 8, the circular droplet generation and capture area 101 sequentially generates droplets and fixes them onto the droplet generation and capture area 101. From… Figure 5 and 6 It can be seen that: ① the size of the droplet generation and capture zone is directly proportional to the size of the generated droplets; ② the higher the flow rate, the smaller the size of the generated and captured droplets. When the flow rate exceeds 0.8 μL / min, droplets will not be generated at the droplet generation and capture zone 101.

[0049] Those skilled in the art will also recognize, or be able to identify, many equivalents of the specific embodiments of the invention described herein using no more than conventional experiments. These equivalents are also included in the appended claims.

Claims

1. A method for in situ generation of microdroplets, characterized in that, The method in which the microdroplets are generated in situ and captured in situ; the microdroplets are generated by a microdroplet generation device, the microdroplet generation device comprising one or more microdroplet generation capture zones (101), the droplet generation capture zone (101) being arranged in a flow-through channel (102), the flow-through channel (102) being provided with a fluid inlet (103) and a fluid outlet (104); When generating water-in-oil microdroplets, the surface of the fluid flow-through region in the flow-through channel (102) is a hydrophobic surface, the contact angle of the hydrophobic surface with water is not less than 90°, the surface of the droplet generation capture zone (101) arranged in the flow-through channel (102) is a hydrophilic surface, the contact angle of the hydrophilic surface with water is at least 40° smaller than the contact angle of the surrounding hydrophobic surface with water; When generating microdroplets, the water phase fluid is driven to fill the microdroplet generation capture zone (101) and the flow-through channel (102) through the fluid inlet (103), and then the injection of the water phase fluid is stopped, and the oil phase fluid is injected into the flow-through channel (102) through the fluid inlet (103), during the process of covering the flow-through channel (102) with the oil phase fluid, the droplet generation capture zone (101) is hydrophilic, which can pull the water phase fluid in the droplet generation capture zone (101), and the water phase fluid not in the droplet generation capture zone (101) will be pushed to the direction of the fluid outlet (104) with the flow of the oil phase fluid; in this process, the water phase fluid can be sheared into microdroplets of a certain size by pulling / pushing away, and finally fixed at the position of the droplet generation capture zone (101); Or, when generating oil-in-water microdroplets, the surface of the fluid flow-through region in the flow-through channel (102) is a hydrophilic surface, the contact angle of the hydrophilic surface with water is not greater than 90°, the surface of the droplet generation capture zone (101) arranged in the flow-through channel (102) is a hydrophobic surface, the contact angle of the hydrophobic surface with water is at least 40° greater than the contact angle of the surrounding hydrophilic surface with water; When generating microdroplets, the oil phase fluid is driven to fill the microdroplet generation capture zone (101) and the flow-through channel (102) through the fluid inlet (103), and then the injection of the oil phase fluid is stopped, and the water phase fluid is injected into the flow-through channel (102) through the fluid inlet (103), during the process of covering the flow-through channel (102) with the water phase fluid, the droplet generation capture zone (101) is hydrophobic, which can pull the oil phase fluid in the droplet generation capture zone (101), and the oil phase fluid not in the droplet generation capture zone (101) will be pushed to the direction of the fluid outlet (104) with the flow of the water phase fluid; in this process, the oil phase fluid can be sheared into microdroplets of a certain size by pulling / pushing away, and finally fixed at the position of the droplet generation capture zone (101).

2. The method of claim 1, wherein, When generating water-in-oil microdroplets, the contact angle of the hydrophobic surface with water is not less than 100°, and the contact angle of the hydrophilic surface with water is not more than 60°.

3. The method of claim 1, wherein, When generating water-in-oil microdroplets, the flow channel (102) is made of a hydrophobic material as a whole, and is only locally treated to be hydrophilic in the droplet generation and capture region (101).

4. The method of claim 3, wherein, The flow channel (102) is made of PDMS.

5. The method of claim 3, wherein, The droplet generation and capture region (101) is locally treated to be hydrophilic by plasma treatment, chemical reagent modification, or chemical liquid deposition.

6. The method of claim 5, wherein, The droplet generation and capture region (101) is locally treated to be hydrophilic by chemical liquid deposition to deposit poly-N-isopropyl acrylamide on the surface of the capture region.

7. The method of claim 1, wherein, The droplet generation and capture region (101) is circular or polygonal.

8. The method of claim 1, wherein, The size of the generated microdroplets is changed by changing the size of the droplet generation and capture region (101), and / or, when generating water-in-oil microdroplets, by changing the flow rate of the oil phase fluid, and when generating oil-in-water microdroplets, by changing the flow rate of the water phase fluid.

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