Microfluidic droplet generation device and method based on channel splitting-capillary site-specific shearing

Abstract

The application discloses a kind of based on passage shunt-capillary fixed-point shearing microfluidic liquid bead preparation device and method, it is related to microfluidic technical field, it includes glass substrate and is set on oil phase shunt module, water phase shearing module and multiple capillary array module on glass substrate, water phase shearing module is set in oil phase shunt module inside, and it is communicated with oil phase shunt module by capillary array module.The application passes through the channel network of tree bifurcation shape and uniformly splits oil phase / water phase fluid into multiple subfluids, simultaneously inserts adjustable glass capillary array as shearing unit in shunt end, by synergic control fluid flow, material viscosity and taper port size etc.Parameter, realize the efficient generation of monodisperse submillimeter to millimeter liquid bead.

Description

Technical Field

[0001] This invention relates to a microfluidic droplet preparation device and method based on channel diversion-capillary fixed-point shearing, belonging to the field of microfluidic technology. Background Technology

[0002] Many active molecules exist in cosmetic formulations. However, some active molecules are sensitive to light, oxygen, temperature and mechanical stress, which can cause them to lose their original activity under normal packaging and storage conditions, resulting in activity decay and reduced efficacy.

[0003] As an ideal carrier for high-value functional molecules such as vitamin C derivatives, retinol, and coenzyme Q10, liquid droplets not only prevent the active ingredients from being directly affected by factors such as oxygen, temperature changes, and mechanical stress, thus maintaining their activity over a long shelf life, but also give the serum a visual aesthetic of "visible microbeads" due to their spherical appearance. Furthermore, the presence of liquid droplets allows them to break and release active ingredients upon application, providing a pleasant skin feel and facilitating the penetration of active substances into the skin along with the external matrix, thereby enhancing product efficacy, safety, and sensory experience.

[0004] In actual production, the encapsulation of active ingredients into droplets often relies on traditional encapsulation techniques such as mechanical stirring and high-pressure homogenization. Although these techniques can achieve throughputs from hundreds of milliliters to liters, the resulting droplets have a wide particle size distribution, poor uniformity, and poor batch-to-batch repeatability. Stirring or high-pressure homogenization processes easily generate high shear forces or high-temperature changes, which can exacerbate the deactivation or decomposition of active ingredients. Consequently, the produced droplets fail to protect the active ingredients and instead become a contributing factor to their deactivation. Furthermore, traditional stirring techniques can cause active ingredients to aggregate under centrifugal force, making it difficult to achieve uniform dispersion in emerging formulations such as transparent serums and anhydrous oil-based agents. This results in cloudy or sticky droplet systems, limiting the functional and aesthetic value of the droplets in the cosmetics field.

[0005] Microfluidic technology for liquid droplets has shown great potential in the generation and manipulation of uniform liquid droplets, providing a new approach for the preparation of cosmetic liquid droplet formulations. However, significant bottlenecks remain in its industrial production. The cosmetic industry has an increasingly prominent sensory demand for "visible microbeads" (particle size > 500 μm). Polydimethylsiloxane (PDMS) chips based on soft lithography technology suffer from insufficient aspect ratio of processing channels and difficulties in handling hydrophilic and hydrophobic properties of some structures, making it difficult to stably generate large-sized liquid droplets.

[0006] While glass capillary microfluidic chips can overcome size limitations by utilizing coaxial flow shearing and improving rigidity, and can flexibly control the hydrophilicity and hydrophobicity of each glass tube surface, they still face significant challenges in high-throughput conversion applications: parallel multi-glass tube channels require an injection pump for each independent channel, causing the cost of peripheral equipment to increase dramatically with the number of channels; glass capillary processing errors, fluid resistance fluctuations, and limitations in pump control accuracy make it difficult to ensure uniformity of flow velocity between channels, resulting in fluctuations in droplet size, which in turn affects the stability of cosmetic formulations and the consistency of skin feel.

[0007] The aforementioned defects and the limited throughput of a single channel together restrict the large-scale production of existing microfluidic droplet technology, making it unable to meet industrial-grade requirements and thus hindering the large-scale application of droplets in cosmetics. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a microfluidic droplet preparation device and method based on channel splitting-capillary point shearing. The oil / water phase fluid is uniformly split into multiple sub-fluids through a tree-like branched channel network. At the same time, an adjustable glass capillary array is embedded at the splitting end as a shearing unit. By synergistically controlling parameters such as fluid flow rate, material viscosity and conical port size, the efficient generation of monodisperse sub-millimeter to millimeter droplets can be achieved.

[0009] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing, comprising a glass substrate, wherein an oil phase splitting module, an aqueous phase shearing module and a plurality of capillary array modules are provided on the glass substrate, wherein the aqueous phase shearing module is disposed inside the oil phase splitting module and is connected to the oil phase splitting module through the capillary array modules; The oil phase splitting module is used to uniformly split the oil phase into oil phase sub-streams and transport them to the capillary array module; the capillary array module is used to transport the oil phase sub-streams in a continuous flow state to the aqueous phase shearing module; the aqueous phase shearing module is used to accelerate the aqueous phase as a continuous phase to directionally impact the oil phase sub-streams, so that the oil phase sub-streams are sheared into monodisperse oil droplets by the aqueous phase.

[0010] Furthermore, the oil phase splitting module includes an oil phase inlet and an oil phase splitting channel. The oil phase inlet is located in the middle of the oil phase splitting channel. The oil phase splitting channel is arch-shaped, and multiple first branch channels are evenly distributed on both sides inside. The first branch channels are connected to the capillary array module.

[0011] Furthermore, the aqueous phase shearing module includes a direct current channel and multiple second branch channels, which are evenly distributed on both sides of the direct current channel. The two ends of the direct current channel are respectively provided with an aqueous phase inlet and an outlet.

[0012] Furthermore, the first branch channels located on both sides of the oil phase split channel and the second branch channels located on both sides of the DC channel are staggered.

[0013] Furthermore, the capillary array module uses glass capillaries, which include an inlet end and an outlet end. The inlet end is connected to the corresponding first branch channel, and the outlet end extends into the corresponding second branch channel and is connected to the second branch channel.

[0014] Furthermore, the outlet end has a suspended micro-nozzle structure.

[0015] In a second aspect, the present invention also provides a processing method for a microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing as described in any of the first aspects, comprising: The channel mold is obtained by cutting out the shapes of the oil phase flow distribution module, the water phase shearing module and multiple capillary array modules from an acrylic plate. The channel mold is bonded to the surface of a glass sheet, and after casting, a microchannel network is obtained. A capillary array is obtained by drawing a capillary tube using a needle drawing device to make one end of the capillary tube tapered, and then opening the tapered shape using a needle forging device. The inner wall of the capillary array is hydrophobically treated to obtain a hydrophobically treated capillary array. After assembling the hydrophobic capillary array with the microchannel network, the array is bonded to a glass substrate by plasma surface treatment, resulting in a microfluidic droplet preparation device based on channel splitting and capillary point shearing.

[0016] Furthermore, the material used for casting is a mixed solution of polydimethylsiloxane and a curing agent; and / or, the hydrophobic treatment uses a toluene solution of trichlorooctadecylsilane.

[0017] Thirdly, the present invention also provides a method for preparing microfluidic droplets based on channel shunting-capillary point shearing, the method being implemented by a microfluidic droplet preparation apparatus based on channel shunting-capillary point shearing as described in any one of the first aspects, comprising: Aqueous solution is injected through the aqueous inlet to purge air from the aqueous shearing module; The oil phase solution is injected through the oil phase inlet, and the injection pressure is gradually increased until a stable oil phase sub-flow is formed; Adjust the pressure difference between the aqueous and oil phase solutions until the monodisperse oil droplets reach the preset size.

[0018] Furthermore, when the injection pressure of the aqueous phase solution is controlled within the range of 0.1~0.3MPa and the injection pressure of the oil phase solution is controlled within the range of 0.08~0.2MPa, the size range of the monodisperse oil droplets is 0.1~1.2mm.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention achieves improvements in active ingredient protection, production efficiency, and system stability through the synergistic innovation of microchannel networks and capillary bridging. It significantly enhances the protection efficiency for photosensitive and heat-sensitive active substances, solves the problem of activity decay caused by thermal energy and mechanical stress, and simultaneously overcomes three major industry bottlenecks: active ingredient damage protection, industrial-grade throughput scale-up, and system stability control. It provides a solution for cosmetic droplet manufacturing that is gentle, efficient, and reliable.

[0020] In terms of production efficiency, this invention utilizes a multi-channel parallel architecture combined with a single pressure source drive design to achieve industrial-scale droplet throughput. By implementing differentiated hydrophilic / hydrophobic surface modifications on the oil / water phase channels, the oil phase forms a stable and continuous film layer within the hydrophobic channels, while the water phase maintains a laminar focused state in the hydrophilic channels. This fundamentally enhances the stability of the two-phase fluid dynamics, laying the foundation for high-throughput continuous operation. The droplet size range is highly controllable, and the synergistic effect of capillary configuration and fluid parameters successfully prepares a highly homogeneous monodisperse system.

[0021] In terms of environmental benefits, this invention significantly reduces carbon emissions through low-temperature and low-pressure processes, and the continuous aqueous phase design effectively reduces solvent dependence, with the overall process meeting green manufacturing standards. Differentiated surface treatment strategies, combined with optimized flow channel geometry, enable the system to maintain flow stability over a wide parameter range, avoiding flow pattern fluctuations and droplet merging common in traditional microfluidics. Continuous operation tests have confirmed its excellent robustness. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a microfluidic liquid droplet preparation device based on channel diversion-capillary fixed-point shearing in one embodiment of the present invention; Figure 2 This is an exploded structural diagram of a microfluidic droplet preparation device based on channel diversion-capillary point shearing in one embodiment of the present invention; Figure 3 This is a schematic diagram of the oil phase splitting module of a microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing in one embodiment of the present invention; Figure 4 This is a schematic diagram of the aqueous phase shearing module of a microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing in one embodiment of the present invention; Figure 5This is a schematic diagram of the capillary array module of a microfluidic droplet preparation device based on channel diversion-capillary point shearing in one embodiment of the present invention; Figure 6 This is a schematic diagram of droplet generation in a microfluidic droplet preparation method based on channel diversion-capillary fixed-point shearing in one embodiment of the present invention, wherein a is a schematic diagram of droplet generation by shearing and b is a schematic diagram of droplet storage. Figure 7 This is a schematic diagram showing the change of droplet size with internal and external phase pressure in a microfluidic droplet preparation method based on channel shunting-capillary fixed-point shearing in one embodiment of the present invention. In the figure: 1-glass substrate, 2-oil phase inlet, 3-aqueous phase inlet, 4-outlet, 5-oil phase splitting module, 6-aqueous phase shearing module, 7-oil phase splitting channel, 8-DC channel, 9-first branching channel, 10-second branching channel, 11-glass capillary. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0024] Example 1

[0025] like Figure 1 and Figure 2 As shown, this embodiment of the invention provides a microfluidic droplet preparation device based on channel splitting-capillary point shearing, including a glass substrate 1. An oil phase splitting module 5, an aqueous phase shearing module 6, and multiple capillary array modules are disposed on the glass substrate 1. In this embodiment, the number of capillary array modules is six. The aqueous phase shearing module 6 is located centrally within the oil phase splitting module 5, and the aqueous phase shearing module 6 and the oil phase splitting module 5 are connected through the capillary array modules.

[0026] like Figure 3 As shown, the oil phase splitting module 5 includes an oil phase inlet 2 and an oil phase splitting channel 7. The oil phase inlet 2 is located at the center of the oil phase splitting channel 7. The oil phase splitting channel 7 is arch-shaped, and multiple first branch channels 9 are evenly distributed on both sides inside. There are 6 first branch channels 9 (corresponding to the capillary array module), which are connected to the corresponding capillary array module respectively.

[0027] In this embodiment, the oil phase diversion module 5 has a length of 55 mm and a width of 40 mm. The oil phase diversion channel 7 includes a circular portion and a straight portion; the diameter of the circular portion is 30 mm, and the length of the straight portion is 36 mm. The diameter of the oil phase inlet 2 is 2 mm. The diameters of the oil phase diversion channel 7 and the first branch channel 9 are both 0.5 mm, and the distance between adjacent first branch channels 9 is 10 mm.

[0028] like Figure 4 As shown, the aqueous phase shearing module 6 includes a DC channel 8 and multiple second branch channels 10. The second branch channels 10 are evenly distributed on both sides of the DC channel 8, and there are 6 second branch channels 10 (corresponding to the capillary array module). An aqueous phase inlet 3 and an outlet 4 are respectively provided at both ends of the DC channel 8.

[0029] In this embodiment, the length of the aqueous phase shearing module 6 is 40 mm and the width is 6 mm. The diameter of the DC channel 8 and the second branch channel 10 is 0.5 mm, and the diameter of the aqueous phase inlet 3 and the outlet 4 is 2 mm.

[0030] It should be noted that the first branch channel 9 located on both sides of the oil phase split channel 7 and the second branch channel 10 located on both sides of the DC channel 8 are staggered.

[0031] like Figure 5 As shown, the capillary array module uses a glass capillary 11, which includes an inlet end and an outlet end. The inlet end is connected to the corresponding first branch channel 9, and the outlet end is a suspended micro-nozzle structure that extends into the corresponding second branch channel 10 and is connected to the second branch channel 10.

[0032] In this embodiment, the vertical portion of the glass capillary 11 has a length of 15 mm, a wall thickness of 0.3 mm, an inner diameter of 0.5 mm at the inlet end, and a length of 1 mm, a wall thickness of 0.1 mm, and an inner diameter of 0.2 mm at the outlet end.

[0033] Example 2

[0034] Based on Example 1, this example provides a processing method for a microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing, specifically including the following steps: The shape of the oil phase diversion channel 7, the direct current channel 8, the first branch channel 9 and the second branch channel 10 are cut out from the acrylic plate to obtain the channel mold.

[0035] The channel mold is bonded to the surface of a glass slide, and the microchannel network is obtained by casting a mixture of polydimethylsiloxane and curing agent at a mass ratio of 9:1.

[0036] One end of the capillary is drawn into a cone shape using a needle pulling device, and the cone part is opened using a needle forging device. The inner wall is then hydrophobically treated with a toluene solution containing 1% by volume of trichlorooctadecylsilane to obtain a hydrophobically treated capillary array.

[0037] The hydrophobic capillary array and microchannel network are assembled, then surface-treated by a channel plasma machine and bonded to a glass substrate to obtain a microfluidic droplet preparation device based on channel diversion-capillary point shearing.

[0038] Example 3

[0039] Based on Example 1, this example provides a method for preparing microfluidic droplets based on channel splitting-capillary point shearing, which includes: The aqueous and oil phase solutions are prepared as follows: In this embodiment, the aqueous solution is prepared by deionized water, glycerol and Tween 80 in a mass ratio of 58:30:2, wherein glycerol is used as a moisturizing and viscosity modifier and Tween 80 is used as a surfactant.

[0040] First, add Tween 80 dropwise to glycerol and magnetically stir at 500 rpm at 40°C until a transparent premixed emulsion is formed. Then, slowly inject deionized water to avoid micelle aggregation and obtain a homogeneous aqueous solution.

[0041] The oil phase solution used 350 cSt silicone oil as a matrix, dissolved 0.05% fat-soluble retinol, and added polydimethylsiloxane (PDMS, 1000 cSt) to adjust the viscosity. Micronized retinol (D90 < 5 μm) and BHT antioxidant were dispersed in a small amount of silicone oil (10% of total volume) under red light, and ultrasonicated at 40 kHz for 30 minutes until completely dissolved. The resulting concentrate was mixed into a silicone oil-PDMS premix matrix and magnetically stirred at 60 °C to form a homogeneous oil phase solution.

[0042] The microfluidic droplet preparation device based on channel splitting-capillary point shearing, with Teflon plastic tubes inserted, was placed on the microscope stage for subsequent experimental observation and debugging.

[0043] Aqueous solution is injected into the aqueous phase shearing module at a pressure of 0.1 MPa from the aqueous phase inlet to purge air from the channel. Simultaneously, oil solution is introduced into the oil phase splitting module from the oil phase inlet, and a gradient pressurization strategy is adopted, that is, the initial pressure is 0.05 MPa to wet the hydrophobic channel, and after 30 seconds it is increased to 0.15 MPa until a stable oil phase sub-flow is formed.

[0044] Combination Figure 7 The injection pressure of the aqueous and oil phase solutions is adjusted, and the pressure difference between the aqueous and oil phase solutions is independently adjusted by a dual-channel pressure controller, thereby achieving the purpose of adjusting the size of the microdroplets. The formation state of the microdroplet size is observed under a microscope.

[0045] The liquid droplets were guided through a polytetrafluoroethylene conduit at the outlet to a nitrogen-protected storage tank. The tank was pre-filled with a 0.1% ascorbate palmitate solution as an antioxidant buffer layer. Under the conditions of an injection pressure of 0.2 MPa for the aqueous phase and 0.08 MPa for the oil phase, the droplet preparation results are as follows: Figure 6 As shown in the figure, uniformly sized droplets are generated at the glass capillary suspension structure. Inside the reagent bottle, the droplets are distinct and there is no fusion between them. The overall throughput can reach 2 L / h.

[0046] This invention allows for droplet size variation ranging from 0.1 to 1.2 mm by adjusting the injection pressure of the aqueous phase solution (0.1~0.3 MPa) and the injection pressure of the oil phase solution (0.08~0.2 MPa). When the inner aqueous phase pressure is fixed, the droplet size increases approximately linearly with increasing outer oil phase pressure; conversely, when the outer oil phase pressure is fixed, the droplet size gradually decreases with increasing inner aqueous phase pressure. Therefore, the droplet size can be highly controlled by adjusting the oil and aqueous phase pressures.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microfluidic droplet preparation device based on channel splitting-capillary point shearing, characterized in that, The device includes a glass substrate, on which an oil phase splitting module, an aqueous phase shearing module, and multiple capillary array modules are disposed. The aqueous phase shearing module is located inside the oil phase splitting module and is connected to the oil phase splitting module through the capillary array modules. The oil phase splitting module is used to uniformly split the oil phase into oil phase sub-streams and transport them to the capillary array module; the capillary array module is used to transport the oil phase sub-streams in a continuous flow state to the aqueous phase shearing module; the aqueous phase shearing module is used to accelerate the aqueous phase as a continuous phase to directionally impact the oil phase sub-streams, so that the oil phase sub-streams are sheared into monodisperse oil droplets by the aqueous phase. The oil phase splitting module includes an oil phase inlet and an oil phase splitting channel. The oil phase inlet is located in the middle of the oil phase splitting channel. The oil phase splitting channel is arch-shaped, and multiple first branching channels are evenly distributed on both sides inside. The first branching channels are connected to the capillary array module. The first branching channels located on both sides inside the oil phase splitting channel and the second branching channels located on both sides of the DC channel are staggered. The aqueous phase shearing module includes a direct current channel and multiple second branch channels. The multiple second branch channels are evenly distributed on both sides of the direct current channel. The two ends of the direct current channel are respectively provided with an aqueous phase inlet and an outlet. The capillary array module uses glass capillaries, which include an inlet end and an outlet end. The inlet end is connected to the corresponding first branch channel, and the outlet end extends into the corresponding second branch channel and is connected to the second branch channel. The outlet end is a suspended micro-nozzle structure. The method for preparing microfluidic droplets using the channel-splitting-capillary point shearing microfluidic droplet preparation device includes: Aqueous solution is injected through the aqueous inlet to purge air from the aqueous shearing module; The oil phase solution is injected through the oil phase inlet, and the injection pressure is gradually increased until a stable oil phase sub-flow is formed; Adjust the pressure difference between the aqueous solution and the oil solution until the monodisperse oil droplets reach the preset size; When the injection pressure of the aqueous solution is controlled within the range of 0.1~0.3MPa and the injection pressure of the oil solution is controlled within the range of 0.08~0.2MPa, the size range of the monodisperse oil droplets is 0.1~1.2mm.

2. A processing method for the microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing as described in claim 1, characterized in that, include: The channel mold is obtained by cutting out the shapes of the oil phase flow distribution module, the water phase shearing module and multiple capillary array modules from an acrylic plate. The channel mold is bonded to the surface of a glass sheet, and after casting, a microchannel network is obtained. A capillary array is obtained by drawing a capillary tube using a needle drawing device to make one end of the capillary tube tapered, and then opening the tapered shape using a needle forging device. The inner wall of the capillary array is hydrophobically treated to obtain a hydrophobically treated capillary array. After assembling the hydrophobic capillary array with the microchannel network, the array is bonded to a glass substrate by plasma surface treatment, resulting in a microfluidic droplet preparation device based on channel splitting and capillary point shearing.

3. The processing method of the microfluidic droplet preparation device based on channel splitting-capillary fixed-point shearing according to claim 2, characterized in that, The material used for casting is a mixed solution of polydimethylsiloxane and a curing agent; and / or, the hydrophobic treatment uses a toluene solution of trichlorooctadecylsilane.

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