A hand-push uniform micro-droplet preparation device and adjustment method

Abstract

The present invention belongs to the field of microfluidics and is a hand-push uniform micro-droplet preparation device, comprising a liquid injection structure and a microfluidic chip. The microfluidic chip is made of a PDMS thin film material. The microfluidic chip is provided with a liquid inlet area, a one-way valve area 1, a one-way valve area 2, a droplet generation area, and a droplet collection area. The liquid inlet area is provided with two liquid inlet flow channels, namely liquid inlet area 1 and liquid inlet area 2. Liquid inlet area 1 and liquid inlet area 2 are respectively connected to one-way valve area 1 and one-way valve area 2. One-way valve area 1 and one-way valve area 2 are connected to the droplet generation area, and the droplet generation area is connected to the droplet collection area. The liquid injection structure is connected to the liquid inlet area. An oil phase fluid is injected into liquid inlet area 1, and an aqueous phase fluid is injected into liquid inlet area 2. The two phases of fluid meet in the droplet generation area and break to generate droplets. The present invention replaces traditional peripheral fluid control equipment such as syringe pumps and pressure controllers through manual control, thereby achieving the preparation of uniformly sized monodispersed micro-droplets, simplifying operation and reducing costs.

Description

Technical Field

[0001] The invention belongs to the field of microfluidics, and in particular relates to a hand-push uniform micro-droplet preparation device and an adjustment method. Background Art

[0002] Microfluidics-based microdroplet preparation has important application value in drug development, bioanalysis, chemical synthesis and other fields. However, how to simply and efficiently prepare a large number of uniformly sized microdroplets remains an urgent problem to be solved.

[0003] The microdroplet generation process in traditional microfluidic chips is often affected by flow fluctuations, resulting in inconsistent droplet size, which in turn affects the accuracy and reliability of experimental results. To address this issue, existing methods typically rely on stable fluid control devices such as syringe pumps and pressure controllers. While these peripheral devices can provide a stable fluid supply, their high cost and complex operating requirements limit their practical application and widespread adoption outside the laboratory. Summary of the Invention

[0004] The present invention aims to provide a hand-push uniform micro-droplet preparation device and adjustment method to solve the above-mentioned technical problems.

[0005] To solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0006] A hand-push uniform micro-droplet preparation device includes a liquid injection structure and a microfluidic chip. The microfluidic chip is made of PDMS thin film material. The microfluidic chip is provided with a liquid inlet area, a one-way valve area 1, a one-way valve area 2, a droplet generation area and a droplet collection area. The liquid inlet area is provided with two liquid inlet flow channels, namely the liquid inlet area 1 and the liquid inlet area 2. The liquid inlet area 1 flows into the oil phase fluid, and the liquid inlet area 2 flows into the water phase fluid; the liquid inlet area 1 and the liquid inlet area 2 are respectively connected to the one-way valve area 1 and the one-way valve area 2. Toward valve area two, the one-way valve area one and the one-way valve area two are connected to the droplet generation area, the droplet generation area is connected to the droplet collection area, and the injection structure is connected to the liquid inlet area. The oil phase fluid is injected into the liquid inlet area one, and the water phase fluid is injected into the liquid inlet area two. The two-phase fluids intersect and break in the droplet generation area to generate droplets; the microdroplets enter the droplet collection area through the liquid inlet channel. When the injection pressure is changed, the deformation effect of the PDMS film changes, and the degree of the one-way valve area one and the one-way valve area two of the valve changes accordingly.

[0007] Furthermore, the injection structure includes a pressure controller and a solution storage container, and the solution storage container contains oil phase fluid, water phase fluid and air. The solution storage container has three hoses, one end of one hose is connected to the pressure controller, and the other end is connected to the air layer in the solution storage container; one end of one hose is connected to the water phase fluid layer in the solution storage container, and the other end is connected to the liquid inlet area 1 of the microfluidic chip; one hose is connected to the oil phase fluid layer in the solution storage container, and the other end is connected to the liquid inlet area 2 of the microfluidic chip, so that the driving of multi-phase fluid is realized by using a single injection structure.

[0008] Furthermore, the pressure controller uses a syringe pump or a gas pressure controller with stable or uneven pressure to drive the fluid.

[0009] Furthermore, the one-way valve area one and the one-way valve area two are arranged on the branches of the liquid inlet channel, and symmetrical valve structures are arranged near the droplet generation area of ​​the two liquid inlet channels. There is a main channel in the middle of the liquid inlet channel, and the valves are symmetrically distributed on both sides of the main channel to form a relative T-structure. The pressure at the input end of the liquid inlet area is set to P0, the pressure at the valve is set to P1, and the pressure in the main channel is set to P2. The normally open direction of the valve structure is forward, and the other direction is reverse. The degree of closing of the valve is controlled by utilizing the pressure difference between points P1 and P2 and the elasticity of PDMS, thereby controlling the liquid inlet flow rate.

[0010] Furthermore, when the fluid flows forward, P0=P1, P2>P0, the PDMS film will deform toward the side with lower pressure due to the pressure difference between P1 and P2, that is, the main channel will become larger; when the fluid flows in the opposite direction, the film will squeeze the injection channel and the main channel will shrink.

[0011] The present invention also discloses an adjustment method for the hand-push uniform micro-droplet preparation device, characterized in that the main channel width is W1, the main channel width at the valve is W2, the PDMS film thickness between the valve and the main channel is W3, the valve channel length is L2, the valve width is L2, the valve is symmetrically distributed according to the main channel, the main channel width W2 at the valve is narrowed, 12μm <W3<20μm,W2<2W3。

[0012] Furthermore, the sensitivity of the valve can be improved by adjusting the length L2 of the valve channel or the membrane thickness W3 at the valve; by adjusting the valve position and structure, the shape of the main channel at the valve is changed to an arc shape, and the shape of the valve is also changed to an arc shape, or the valve is designed at the corner of the channel to improve the valve closing degree.

[0013] Furthermore, the droplet generation area adopts a T-shaped channel structure, the two-phase fluids converge at the T-junction, and the aqueous phase fluid generates droplets under the shearing action of the oil phase fluid, completing the preparation of microdroplets; the droplet generation area is provided with multiple parallel T-shaped structures to improve the droplet generation flux; and the aqueous phase flow is evenly distributed by designing the flow resistance of each channel.

[0014] Furthermore, the droplet generation flux is improved by setting a symmetrical oil phase channel.

[0015] Furthermore, the T-shaped channel structure is replaced by a flow focusing structure.

[0016] The hand-push uniform micro-droplet preparation device and adjustment method of the present invention have the following advantages:

[0017] The valve structure design of the device ensures that even if the hand push pressure changes, the droplet size can still be maintained within a certain range, reducing the impact of flow fluctuations on droplet size.

[0018] The one-way valve has a simple structure and no moving parts. Unlike other active valve structures, it does not require an additional actuator. It also responds quickly to changes in injection pressure, ensuring stable flow.

[0019] The device is designed to be handheld or portable, does not require complicated equipment and operations, is easy to use under different laboratory or field conditions, lowers the threshold for use, and is easy to promote and popularize. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the device of the present invention.

[0021] Figure 2a It is a schematic diagram of valve shape design;

[0022] Figure 2b This is a schematic diagram of the valve design at the corner of the channel;

[0023] Figure 2c The valve is designed as an arc diagram;

[0024] Figure 3 This is a channel design diagram of a multi-T structure

[0025] Figure 4 This is a symmetrical oil phase channel design diagram

[0026] Figure 5 Schematic diagram of different droplet generation structure designs

[0027] Figure 6 This is the relationship between the forward and reverse flow rates and the injection pressure in Example 1.

[0028] Figure 7 In Example 1, the valve closing degree under different pressures

[0029] Figure 8 This is the droplet size distribution diagram in Example 2

[0030] Figure 9 This is the droplet size distribution diagram in Example 3

[0031] Explanation of the markings in the figure: 1. Liquid injection structure; 1-1. Pressure controller; 1-2. Solution storage container; 2. Microfluidic chip; 2-1. Liquid inlet area 1; 2-2. Liquid inlet area 2; 2-3. Droplet generation area; 2-4. Droplet collection area; 2-5. One-way valve area 1; 2-6. One-way valve area 2. DETAILED DESCRIPTION

[0032] In order to better understand the purpose, structure and function of the present invention, the hand-push uniform micro-droplet preparation device and adjustment method of the present invention are further described in detail below with reference to the accompanying drawings.

[0033] The present invention discloses a hand-push device for preparing uniform micro-droplets, comprising a liquid injection structure 1 and a microfluidic chip 2. The microfluidic chip 2 is made of a PDMS thin film material and is provided with a liquid inlet area, a one-way valve area 1 2-5, a one-way valve area 2-6, a droplet generation area 2-3, and a droplet collection area 2-4. The liquid inlet area is provided with two liquid inlet flow channels, namely, the one-way valve area 1 2-1 and the two-way valve area 2-2. The oil phase fluid flows into the one-way valve area 1 2-1, while the water phase fluid flows into the two-way valve area 2-2. The one-way valve area 1 2-1 and the two-way valve area 2-2 are connected to the one-way valve area 1 2-5 and the one-way valve area 2 2-6, respectively. The one-way valve area 1 2-5 and the one-way valve area 2 2-6 are connected to the droplet generation area 2-3, and the droplet generation area 2-3 is connected to the droplet collection area 2-4. The injection structure 1 is connected to the liquid inlet area, and the oil phase fluid is injected into the liquid inlet area 1 2-1, and the water phase fluid is injected into the liquid inlet area 2-2. The injection structure 1 includes a pressure controller 1-1 and a solution storage container 1-2. The solution storage container 1-2 contains oil phase fluid, water phase fluid, and air. The solution storage container 1-2 has three hoses: one hose is connected to the pressure controller 1-1 at one end and connected to the air layer in the solution storage container 1-2 at the other end; one hose is connected to the water phase fluid layer in the solution storage container 1-2 at one end and connected to the liquid inlet area 1 2-1 of the microfluidic chip 2; and one hose is connected to the oil phase fluid layer in the solution storage container 1-2 and connected to the liquid inlet area 2 2-2 of the microfluidic chip 2 at the other end. In this case, a single injection structure 1 can achieve multi-phase fluid driving. The pressure controller 1-1 can use a stable pressure injection pump or air pressure controller to drive the fluid. The pressure controller 1-1 can also use an uneven injection source, such as a hand-push type.

[0034] The two-phase fluids converge and break apart in the droplet generation zone 2-3, forming droplets. The microdroplets enter the droplet collection zone 2-4 through the liquid inlet channel. One-way valve zone 1 2-5 and one-way valve zone 2 2-6 are located on branches of the liquid inlet channel. Symmetrical valve structures are installed near the droplet generation zone 2-3 in both liquid inlet channels. A main channel is located in the middle of the liquid inlet channel, and valves are symmetrically distributed on both sides of the main channel, forming a relative T-shaped structure. The pressure at the input end of the liquid inlet zone is P0, the pressure at the valve is P1, and the pressure in the main channel is P2. The valve structure's normally open direction is the forward direction, and the other direction is the reverse direction. The valve's degree of closure, and thus the liquid inlet flow rate, is controlled by utilizing the pressure difference between points P1 and P2 and the elasticity of the PDMS. When the fluid flows in the forward direction, the pressures at various points within the channel follow this relationship: P0 = P1, P2 > P0. Therefore, the pressure differential between P1 and P2 causes the PDMS film to deform toward the lower pressure side, expanding the main channel. When the fluid flows in the reverse direction, the film squeezes the injection channel, shrinking it. Changing the injection pressure alters the PDMS film's deformation, and the degree of closure of both one-way valve sections 1-5 and 2-6 changes accordingly.

[0035] The main channel width is W1, and the main channel width at the valve is W2. The PDMS film thickness between the valve and the main channel is W3. The valve channel length is L2, and the valve width is L2. The valves are symmetrically distributed around the main channel, and the main channel width W2 is narrowed at the valve.

[0036] Because the thickness of the PDMS film W3 between the valve and the main channel is thin, it is easy to deform and difficult to break. Therefore, a 12 μm <W3<20μm,W2<2W3。

[0037] By adjusting the length L2 of the valve channel, the sensitivity of the valve can be improved.

[0038] By adjusting the film thickness W3 at the valve, the sensitivity of the valve can be improved.

[0039] like Figure 2b As shown, adjust the valve position and structure, change the valve design shape, design the valve at the corner of the channel to improve the valve closing degree.

[0040] like Figure 2c As shown, changing the shape of the main channel at the valve into an arc shape and also changing the shape of the valve into an arc shape can improve the closing degree of the valve.

[0041] Preferably, the droplet generation area 2-3 adopts a T-shaped channel structure, the two-phase fluids meet at the T-junction, and the water phase fluid generates droplets under the shearing action of the oil phase fluid, completing the preparation of micro droplets. Figure 3As shown, the droplet generation area 2-3 can be provided with multiple parallel T-shaped structures to improve the droplet generation flux. At the same time, appropriate flow resistance is designed for each channel to evenly distribute the water phase flow.

[0042] like Figure 4 As shown, a symmetrical oil phase channel is set to improve the droplet generation flux.

[0043] like Figure 5 As shown, the T-channel structure can be replaced by a flow focusing structure, etc.

[0044] During use, different air pressures were set to drive the fluid, and the valve state and flow rate were recorded. A high-speed camera was used to record the droplet formation process in droplet generation areas 2-3, measuring and calculating the droplet size and generation frequency at different driving pressures. Example 1

[0045] The microfluidic chip 2 is a PMDS microfluidic chip. The chip production process includes CAD-based chip functional pattern design, photolithography, development, PDMS molding, punching, plasma bonding and other steps.

[0046] The designed microfluidic chip structure, such as Figure 1 As shown in the figure, the main channel width W1 is 50 μm, and the channel width W2 at the valve is 25 μm. The valves are symmetrically located on both sides of the channel. The PDMS film thickness W3 between the valve and the main channel is 16 μm, and the valve channel length L2 is 1500 μm. The valve structure has a thickness of 30 μm, and the valve width L1 is 250 μm.

[0047] According to the designed pattern, photolithography is performed. A photoresist with a thickness of 100um is spin-coated on the surface of a clean silicon wafer. After coating, a pre-bake treatment is performed for 30 minutes. The silicon wafer is then cooled to room temperature and placed in a DMD maskless photolithography machine for exposure according to the imported channel drawing. After the exposure is completed, it is post-baked at 95°C for 5 minutes. The silicon wafer is then taken out and developed in a developer for 20 minutes. The development process is carried out on a horizontal shaker. After development is completed, the silicon wafer is rinsed with acetone 2-3 times and then blown dry. The photolithographic silicon wafer is placed in a culture dish. The PDMS prepolymer and the cross-linking agent are mixed in a ratio of 10:1, poured into the culture dish, vacuumed to remove bubbles, and then placed in an oven for baking at 65°C for 1 hour. After the baking is completed, the PDMS is carefully removed, and after drilling, it is bonded to the glass using a plasma machine.

[0048] Pressure controller 1-1 drives fluid into microfluidic chip 2 to achieve flow conditions at different injection pressures. The specific structural design is as follows: the fluid is placed in solution storage container 1-2, which is equipped with three hoses: two of which serve as fluid outlets connected to the liquid inlet of microfluidic chip 2, and the other hose is connected to pressure controller 1-1 to drive the fluid.

[0049] The normal open direction of the valve is defined as the forward direction, and the other direction is the reverse direction. When the fluid flows forward, P1 > P2, and the channel at the valve expands under the action of the pressure difference; when the fluid flows in the reverse direction, P1 < P2, and the main channel at the valve is squeezed and becomes smaller under the action of the pressure difference. At different injection pressures, the flow rates are different, and the deformation degrees of the main channel are also different.

[0050] The oil-phase fluid is isopropyl palmitate (added with 7% EM180 surfactant), and the water-phase fluid is deionized water. The valve states and flow rates in the forward and reverse directions are measured respectively at injection pressures of 250 mbar, 500 mbar, 750 mbar, and 1000 mbar.

[0051] As Figure 6 shows the valve states in the forward and reverse directions at different injection pressures. The corresponding Figure 7 shows the flow rates in the forward and reverse directions at different injection pressures. Example Two

[0052] Design a microfluidic chip 2 structure with a double-channel as Figure 1 shown. The width W1 of the main channel is 50 μm, and the width W2 of the channel at the valve is 25 μm. The valves are symmetrically distributed on both sides of the main channel. The thickness W3 of the PDMS film between the valve and the main channel is 16 μm, and the length L2 of the valve channel is 6000 μm. The thickness of the valve structure is 30 μm, and the width L of the valve is 250 μm.

[0053] The normal open direction of the valve is defined as the forward direction, and the other direction is the reverse direction. Use a pressure controller 1-1 to drive the fluid into the microfluidic chip 2. The specific structural design is as follows: The two-phase fluid is filled in a solution storage container 1-2. The solution storage container 1-2 is provided with three hoses. One hose is used as the outlet end of the oil-phase fluid and is connected to the liquid inlet of the microfluidic chip 2, one hose is used as the outlet end of the water-phase fluid and is connected to the liquid inlet of the microfluidic chip 2, and the other hose is connected to the pressure controller 1-1 to drive the fluid. The oil-phase fluid is isopropyl palmitate (added with 7% EM180 surfactant), and the water-phase fluid is deionized water.

[0054] The droplet generation area 2-3 adopts a T-shaped channel structure. The two-phase fluids converge at the T-shaped junction, and the water-phase fluid breaks under the shearing of the oil-phase fluid to generate droplets.

[0055] Set the pressure value of the pressure controller 1-1 to 200 mbar, and use a high-speed camera to record the process of droplet generation and the droplet morphology. At this time, the average size of the droplets is 243 μm, and the coefficient of variation CV = 0.61% (CV = (standard deviation / average value * 100%)). The droplet size distribution diagram is as Figure 8 shown. Example Three

[0056] Design a dual-channel microfluidic chip 2 structure, such as Figure 1 As shown in the figure, the main channel width W1 is 50 μm, and the channel width W2 at the valve is 25 μm. The valves are symmetrically located on both sides of the channel. The PDMS film thickness W3 between the valve and the main channel is 16 μm, and the valve channel length L2 is 6000 μm. The valve structure has a thickness of 30 μm, and the valve width L2 is 250 μm.

[0057] The normally open direction of the valve is considered forward, and the other direction is considered reverse. Pressure controller 1-1 drives the fluid into microfluidic chip 2. The specific structural design is as follows: the two-phase fluid is placed in solution storage container 1-2. Solution storage container 1-2 is equipped with three flexible hoses: one for the oil phase fluid outlet connected to the liquid inlet of microfluidic chip 2, one for the water phase fluid outlet connected to the liquid inlet of microfluidic chip 2, and the third flexible hose connected to microfluidic chip 2 to drive the fluid. The oil phase fluid is isopropyl palmitate (with 7% EM180 surfactant added), and the water phase fluid is deionized water.

[0058] The droplet generation adopts a T-shaped channel structure. The two-phase fluids meet at the T-junction, and the water phase fluid breaks under the shear of the oil phase fluid to generate droplets.

[0059] The pressure controller 1-1 was set to 500 mbar, and a high-speed camera was used to record the droplet generation process and droplet morphology. The average droplet size was 249 μm, and the coefficient of variation (CV) was 0.68% (CV = (standard deviation / average value * 100%)). The droplet size distribution is shown in Figure 2. Figure 9 shown.

[0060] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A hand-push uniform micro-droplet preparation device, comprising a liquid injection structure (1) and a microfluidic chip (2), wherein the microfluidic chip (2) is made of a PDMS thin film material, characterized in that: The microfluidic chip (2) is provided with a liquid inlet area, a one-way valve area 1 (2-5), a one-way valve area 2 (2-6), a droplet generation area (2-3) and a droplet collection area (2-4). The liquid inlet area is provided with two liquid inlet flow channels, namely the liquid inlet area 1 (2-1) and the liquid inlet area 2 (2-2). The liquid inlet area 1 (2-1) flows into the oil phase fluid, and the liquid inlet area 2 (2-2) flows into the water phase fluid; the liquid inlet area 1 (2-1) and the liquid inlet area 2 (2-2) flow into the water phase fluid. The second liquid area (2-2) is connected to the one-way valve area (2-5) and the one-way valve area (2-6) respectively. The one-way valve area (2-5) and the one-way valve area (2-6) are connected to the droplet generation area (2-3). The droplet generation area (2-3) is connected to the droplet collection area (2-4). The injection structure (1) is connected to the liquid inlet area. The oil phase fluid is injected into the liquid inlet area (2-1) and the water phase fluid is injected into the liquid inlet area (2-2). The two-phase flow The bodies intersect and break in the droplet generation area (2-3) to generate droplets; the microdroplets enter the droplet collection area (2-4) through the liquid inlet flow channel, and when the injection pressure is changed, the deformation effect of the PDMS film changes, and the film deformation degree of the one-way valve area 1 (2-5) and the one-way valve area 2 (2-6) of the valve changes accordingly; the one-way valve area 1 (2-5) and the one-way valve area 2 (2-6) are arranged on the branch of the liquid inlet flow channel, and a symmetrical valve structure is arranged near the droplet generation area (2-3) of the two liquid inlet flow channels, and a main channel is provided in the middle of the liquid inlet flow channel. The valves are symmetrically distributed on both sides of the main channel to form a relative T-shaped structure, and the pressure at the input end of the liquid inlet area is set as P0, the pressure at the valve is set as P1, and the pressure of the main channel is set as P2. The normally open direction of the valve structure is recorded as forward, and the other direction is recorded as reverse. The closing degree of the valve is regulated by utilizing the pressure difference between points P1 and P2 and the elasticity of PDMS, thereby regulating the liquid inlet flow rate.

2. The hand-push uniform micro-droplet preparation device according to claim 1, characterized in that: The injection structure (1) includes a pressure controller (1-1) and a solution storage container (1-2). The solution storage container (1-2) contains an oil phase fluid, an aqueous phase fluid and air. The solution storage container (1-2) has three hoses, one end of which is connected to the pressure controller (1-1) and the other end is connected to the air layer in the solution storage container (1-2); one end of which is connected to the aqueous phase fluid layer in the solution storage container (1-2) and the other end is connected to the first liquid inlet area (2-1) of the microfluidic chip (2); and one hose is connected to the oil phase fluid layer in the solution storage container (1-2) and the other end is connected to the second liquid inlet area (2-2) of the microfluidic chip 2, so that the driving of multiphase fluid is realized by using a single injection structure (1).

3. The hand-push uniform micro-droplet preparation device according to claim 2, characterized in that: The pressure controller (1-1) drives the fluid using a syringe pump or a gas pressure controller with stable or uneven pressure.

4. A method for adjusting the hand-push uniform micro-droplet preparation device according to any one of claims 1 to 3, characterized in that: Assume that the width of the main channel is W1, the width of the main channel at the valve is W2, the thickness of the PDMS film between the valve and the main channel is W3, the valve is symmetrically distributed according to the main channel, and the width of the main channel at the valve is narrowed to 12μm. <W3<20μm,W2<2W3。

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