Microfluidic chips, methods, and applications based on gravity-captured droplets

Abstract

This application provides a microfluidic chip, method, and application for gravity-based droplet capture. The chip includes: a microfluidic chip body; microchannels located inside the microfluidic chip body, with both ends connected to the chip channel inlet or outlet, respectively, for droplet inflow and outflow; droplet capture units, which are circular tunnel units arrayed within the microchannels for capturing droplets under gravity; and a microfluidic chip cover plate covering the microfluidic chip body, tightly fitted to form a closed microchannel space. In this way, continuous droplet capture can be maintained without the need for continuous external force, enabling high-throughput continuous droplet capture and release, which is beneficial for large-scale droplet-related research and applications.

Description

Technical Field

[0001] This application relates to the field of microfluidic chip technology, and in particular to microfluidic chips, methods and applications based on gravity-captured droplets. Background Technology

[0002] Microfluidic chips, serving as "lab-on-a-chip" solutions, are the core platform of microfluidic technology and have wide applications in numerous fields. They offer advantages such as low sample consumption, ease of operation, small size, and portability, and can also achieve multifunctional integration. At the micro- and nanoscale, microfluidic chips can manipulate immiscible two-phase solutions to generate micro-liquid units, i.e., tiny droplets, and perform operations such as droplet generation, splitting, merging, mixing, and trapping, bringing new research and application ideas to fields such as chemical synthesis, bioanalysis, drug screening, and materials science.

[0003] In microfluidics, water-in-oil (W / O) and oil-in-water (O / W) droplets are important emulsion systems, playing a crucial role in food processing, cosmetics, and pharmaceutical research and development. However, traditionally prepared W / O and O / W droplets exhibit wide size distributions and poor stability, significantly limiting their development and utilization. With the advancement of microfluidics and nanotechnology, significant progress has been made in related research and applications. Microfluidics can not only precisely prepare monodisperse droplets but also develop emulsion systems with specific functions by adjusting droplet composition and structure. Effective capture and manipulation of droplets facilitate in-depth research into their interfacial behavior, thereby improving the efficiency of developing stable W / O and O / W droplets.

[0004] Currently, droplet capture technology mainly relies on external force fields, such as electric fields, magnetic fields, or acoustic fields. These technologies achieve droplet capture by applying external energy, but they have many problems in practical applications:

[0005] Complex operation and high cost: Droplet manipulation techniques that rely on external force fields typically require sophisticated and expensive equipment, and the operating procedures are also quite complex. This not only increases the difficulty of experiments but also limits their application in rapid detection and on-site analysis, making them difficult to promote in resource-constrained environments.

[0006] Poor biocompatibility and insufficient stability: Strong field environments such as electric and magnetic fields can damage biological samples, such as causing cell membrane electroporation or protein denaturation, which limits the application of this technology in the biomedical field. In addition, the instability of the external force field can lead to poor repeatability of droplet manipulation, affecting the accuracy and reliability of experimental results.

[0007] Droplets are easily deformable and difficult to capture continuously: When using an external force field to capture droplets, the droplets may be squeezed, and once the external force is removed, the captured droplets will quickly escape from the chip, making it impossible to capture droplets continuously.

[0008] Therefore, there is an urgent need to develop a new droplet capture and manipulation technology that does not rely on external force fields. Summary of the Invention

[0009] To address the issue that the precise capture and manipulation of droplets currently relies mainly on external force fields, this application provides a microfluidic chip, method, and application for gravity-based droplet capture, aiming to utilize the microstructure in the chip to achieve droplet capture, release, and in-situ observation within the chip.

[0010] According to a first aspect of this application, a microfluidic chip based on gravity-captured droplets is provided, comprising:

[0011] Microfluidic chip body;

[0012] The microchannel is located inside the microfluidic chip body, and its two ends are connected to the chip channel inlet or outlet, respectively. The chip channel inlet or outlet is used for the inflow and outflow of droplets.

[0013] A droplet capturing unit, wherein the droplet capturing unit is a circular tunnel unit arrayed in a microchannel, used to capture droplets under the action of gravity;

[0014] A microfluidic chip cover plate covers the microfluidic chip body and fits tightly against the microfluidic chip body to form a closed microchannel space.

[0015] Furthermore, the microchannels and droplet capturing units are hydrophilic or hydrophobic.

[0016] Furthermore, the material of the chip is selected from one or more combinations of the following categories:

[0017] Polymer materials include, but are not limited to, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), polydimethylsiloxane-vinylsiloxane copolymer, polycarbonate (PC), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polypropylene (PP), polyimide (PI), thermoplastic polyurethane (TPU), cyclic olefin copolymer (COC), polystyrene (PS), polyetheretherketone (PEEK), or hydrogels;

[0018] Inorganic materials: including but not limited to glass, metals, ceramics or their surface-functionalized modified materials;

[0019] Composite materials: including polymer-based nanocomposites, paper-based materials, 3D printing materials, or metal-polymer laminates.

[0020] Furthermore, the microfluidic chip also includes a substrate located at the bottom of the microfluidic chip to support the entire chip.

[0021] Furthermore, the surface properties and structural size of the chip microchannel and droplet capturing unit can be customized according to the properties and size of the droplets. When the chip microchannel and droplet capturing unit are hydrophilic, they can capture oil-in-water droplets or multiple droplets with an outermost aqueous solution.

[0022] When the chip microchannels and droplet capture units are hydrophobic, it is possible to capture water-in-oil droplets or multiple droplets whose outermost layer is an organic solution.

[0023] Furthermore, the hydrophobicity of the chip can be obtained through hydrophobic modification, wherein the hydrophobic modification is that the molecular structure of the hydrophobic modifier includes groups that can chemically react with the substrate surface and groups that provide hydrophobic properties. The hydrophobic modifier includes one or more of silane reagents and fluorinated reagents.

[0024] The silane includes one or more of fluorinated silanes, long-chain alkyl silanes, and functionalized silanes; the fluorinated silane is a C3~C-chain perfluorinated alkyl chain. 18 Silanes; long-chain alkylsilanes are C-containing 12 ~C 18 Silanes with alkyl chains; functionalized silanes are silanes containing active groups such as amino, epoxy, and thiol groups; fluorinating agents include one or more of fluorocarbon compounds, fluorinated polymers, and fluoride ions.

[0025] Furthermore, methods for making the chip hydrophilic include one or more of plasma treatment, ultraviolet / ozone treatment, silane coupling agent treatment, and physical coating of a hydrophilic layer;

[0026] The gases used in the plasma treatment include one or more of oxygen, argon and nitrogen, and the silane coupling agent used in the silane coupling agent treatment is trimethyl[3-(2-methoxy)propyl]silane.

[0027] The reagents coated in the physical coating hydrophilic layer include one or more of polyvinyl alcohol, polyethylene glycol, chitosan, and polydopamine.

[0028] Furthermore, the microfluidic chip also possesses multi-scale capture capabilities, targeting fluid substances, solid / semi-solid materials, and other micro / nano-scale functional units. Fluid substances include water-in-oil and oil-in-water monoemulsion droplets and their multiple emulsion droplets; solid / semi-solid materials include microgel particles, polymer microspheres, and inorganic / organic nanoparticles; and other micro / nano-scale functional units.

[0029] According to a second aspect of this application, a droplet capture method is provided, which employs the microfluidic chip for capturing droplets based on gravity as described above, wherein the droplet is an oil-in-water droplet, a water-in-oil droplet, or other multiple droplets that will sink under the action of gravity.

[0030] According to a third aspect of this application, a droplet release method is provided, which uses the microfluidic chip described above for gravity-based droplet capture to release the captured droplets from the droplet capture unit. The droplets are water-in-oil droplets, oil-in-water droplets, or other multiple droplets that sink under gravity.

[0031] According to the fourth aspect of this application, a method for in-situ observation of droplets is provided, which uses the microfluidic chip based on gravity-captured droplets described above to perform in-situ observation of water-in-oil droplets or oil-in-water droplets.

[0032] According to the fifth aspect of this application, an application of a microfluidic chip based on gravity-captured droplets is provided, which can be applied to the research and development of droplets and microgels in fields including food, pharmaceuticals, health products, basic scientific research, and life sciences, as well as droplet microreactions and microdetection.

[0033] Compared to existing technologies, the beneficial effects of this application are:

[0034] This disclosure utilizes the microstructure in a microfluidic chip to capture and release droplets within the chip. The operation is simple, and the droplet can be continuously captured without the need for continuous external force. It also enables easy and accurate in-situ observation of the droplets.

[0035] When used in series with other microfluidic chips, it can enable precise dynamic observation of droplet generation, splitting, merging, and rupture. It can be used for droplet research and development in life sciences or basic research fields such as food, pharmaceuticals, and health products, and can also be extended to droplet micro-reactions and micro-detection.

[0036] Furthermore, the structure and surface properties of the microchannels and droplet capture units of the chip described in this disclosure can also be customized according to the size and type of the captured object, so as to achieve the capture of droplets, gels and microspheres of different properties and sizes. Attached Figure Description

[0037] The above and other features, advantages, and aspects of the embodiments of this application will become more apparent from the accompanying drawings and the following detailed description. The drawings are provided for a better understanding of the invention and are not intended to limit the scope of the application. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0038] Figure 1 A schematic diagram of a microfluidic chip structure based on gravity-captured droplets according to an embodiment of this application is shown;

[0039] Figure 2 A flowchart illustrating the manufacturing scheme of a microfluidic chip based on gravity-captured droplets according to an embodiment of this application is shown;

[0040] Figure 3 A schematic diagram of the water-in-oil droplet capture results according to an embodiment of this application is shown;

[0041] Figure 4 A schematic diagram of in-situ observation results after water-in-oil droplet capture according to an embodiment of this application is shown;

[0042] Figure 5 A schematic diagram of the water-in-oil droplet capture results according to an embodiment of this application is shown;

[0043] Figure 6 A schematic diagram of in-situ observation results after water-in-oil droplet capture according to an embodiment of this application is shown;

[0044] Wherein, 1: substrate; 2: chip flow channel inlet or outlet; 3: droplet capture unit; 4: chip cover plate; 5: chip microchannel; 6: chip body. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0046] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0047] Example 1: This application proposes a microfluidic chip based on gravity-captured droplets, such as... Figure 1 As shown, (A) is a schematic diagram of the 2D structure of the chip, (B) is a partial enlarged view of the 2D structure of the chip, (C) is a physical image of the chip, and (D) is a simulation diagram of the 3D structure of the chip.

[0048] The microfluidic chip consists of a chip channel inlet or outlet 2, a droplet capture unit 3, a chip cover plate 4, a microchannel 5, and a microfluidic chip body 6.

[0049] Among them, the flow channels are distributed at both ends of the microchannels, forming the chip's inlet or outlet. Figure 1 (A), (C) and (D)), the droplet-capturing microstructure is an array of circular tunnel units distributed in the microchannels ( Figure 1 (B) and (D)).

[0050] Preferably, the microfluidic chip further includes a substrate 1 located at the bottom of the microfluidic chip 6 to support the entire chip.

[0051] Preferably, the material of the chip is:

[0052] Polymer materials include, but are not limited to, polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), polydimethylsiloxane-vinylsiloxane copolymer, polycarbonate (PC), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polypropylene (PP), polyimide (PI), thermoplastic polyurethane (TPU), cyclic olefin copolymer (COC), polystyrene (PS), polyetheretherketone (PEEK), or hydrogels;

[0053] Inorganic materials: including but not limited to glass, metals, ceramics or their surface-functionalized modified materials;

[0054] Composite materials include polymer-based nanocomposites (such as graphene / PDMS), paper-based materials (hydrophobic cellulose materials), 3D printing materials (photosensitive resins, bio-inks), or metal-polymer laminates.

[0055] Other materials: Other materials with similar processing properties, chemical stability or biocompatibility to the above materials are suitable for the manufacture of microfluidic chips.

[0056] In a preferred embodiment, the microchannel 5 and the droplet capturing unit 3 are hydrophobic or hydrophilic.

[0057] Example 2: This example provides a manufacturing scheme for a microfluidic chip based on gravity-captured droplets, as detailed below:

[0058] like Figure 2 As shown, the fabrication scheme for a microfluidic chip based on gravity-captured droplets includes three steps: soft lithography, chip molding, and chip bonding.

[0059] (1) Soft lithography

[0060] Take a wafer and place it on a spin coater. Pour an appropriate amount of photoresist onto the wafer and run the spin coater according to the set parameters to evenly coat the photoresist onto the wafer surface. After spin coating, transfer the wafer to a heated stage and perform a soft bake program (bake the wafer at 95℃ in the dark for 5-10 minutes) until the photoresist on the wafer is cured. After soft bake, transfer the wafer to a photolithography machine and run the photolithography program to etch the chip channels onto the photoresist. After photolithography, transfer the wafer to a heated stage and bake the wafer at 95℃ in the dark for 5-10 minutes for hardening. After hardening, spin coat the photoresist onto the wafer again and perform the soft bake and photolithography programs again to etch the microdroplet capture units within the chip channels. After etching, transfer the wafer back to the heated stage and perform the hardening program. After hardening, the photoresist on the wafer is rinsed with developer to remove excess photoresist, exposing the chip channels and droplet capture units. The wafer is then transferred to a heating stage for hard baking (baking the wafer at 95°C in the dark for 5-10 minutes) to obtain the chip template.

[0061] (2) Chip molding

[0062] As described in Example 1, there are multiple choices of chip materials. Therefore, depending on the selected material, a suitable chip molding process must be employed. Specifically,

[0063] a. Polymer materials (such as PDMS, PMMA, COC, etc.)

[0064] Place the etched chip template into a petri dish. If using PDMS, mix PDMS and curing agent at a 10:1 mass ratio and pour the mixture into the petri dish, allowing the PDMS to spread evenly on the chip template. Then, place the petri dish in a vacuum chamber for degassing. After degassing, place the petri dish in an oven and heat at 65°C until the PDMS is completely hardened. Cut the hardened PDMS off the chip to obtain the PDMS droplet capture chip template. If using thermoplastic materials (such as PMMA or COC), use an injection molding process, injecting the molten material into the template and then demolding after cooling.

[0065] b. Inorganic materials (such as glass)

[0066] Microchannels and droplet trapping units are directly etched onto the material surface using wet etching or laser micromachining techniques, based on the template structure.

[0067] c. Composite materials (such as 3D printing materials)

[0068] 3D printing materials (such as photosensitive resin) can be used to directly build chip structures layer by layer through photopolymerization 3D printing technology.

[0069] (3) Chip bonding

[0070] If using PDMS, take a PDMS cover plate of appropriate size without any texture. Figure 1 (C) in the middle), the control is in the droplet capture chip body ( Figure 1 (C) Two-channel inlet ( Figure 1 An opening is made at (C) in the middle. Then, they are placed together with the substrate into an oxygen plasma cleaner. After running the plasma cleaning program, the PDMS cover plate and the chip body are bonded together, and then they are bonded together to the substrate to obtain a complete droplet capture chip.

[0071] According to the embodiments of this application, the following beneficial effects are achieved:

[0072] (1) Soft lithography can precisely etch chip channels and microdroplet capture units on photoresist through multiple spin coating, photolithography, baking and other steps, ensuring the fineness and accuracy of the microstructure and laying the foundation for subsequent stable droplet capture. For example, the precise microstructure size can be customized according to different droplet sizes to improve capture efficiency.

[0073] (2) During the casting process of PDMS chip template, the ratio of PDMS to curing agent, vacuum degassing and heating hardening conditions are strictly controlled so that PDMS can uniformly cover the chip template and form a high-quality chip main template, reducing internal bubbles and defects, and improving the physical properties and service life of the chip.

[0074] Example 3: This example provides a hydrophobic or hydrophilic modification scheme for a microfluidic chip based on gravity-captured droplets, as detailed below:

[0075] (1) Chip hydrophobic modification scheme

[0076] The complete droplet capture chip obtained in Example 2 was placed in a plasma cleaner and the plasma cleaning program was run. After the program finished running, a hydrophobic modifier was injected into the chip's microchannels. After reacting for a period of time, excess hydrophobic modifier in the channels was flushed away. This yields a highly hydrophobic droplet capture chip that can be used to capture water-in-oil droplets.

[0077] The hydrophobic modifier includes one or more of silane reagents and fluorinated reagents.

[0078] Furthermore, the silane includes one or more of fluorinated silanes, long-chain alkyl silanes, and functionalized silanes.

[0079] Furthermore, the fluorinated silane is a C3~C-containing perfluoroalkyl chain. 18 Silanes (such as tridecafluorooctyltriethoxysilane); fluorinated silanes are C3~C6 alkyl chains containing perfluoroalkyl groups. 18 Silanes (such as tridecafluorooctyltriethoxysilane); long-chain alkylsilanes are C-containing12 ~C 18 Alkyl chain silanes (such as octadecyltrimethoxysilane); functionalized silanes are silanes containing active groups such as amino, epoxy, and mercapto groups (such as aminopropyltriethoxysilane).

[0080] Furthermore, the fluorinating agent includes one or more of fluorocarbon compounds, fluorinated polymers, and fluoride ion solutions.

[0081] (2) Chip hydrophilic modification scheme

[0082] Plasma treatment: The droplet capture chip bonded in Example 2 is placed in a plasma cleaner, and a gas (one or more of oxygen, argon or nitrogen) is introduced. After running the plasma cleaning program, water is injected into the chip channel to make the droplet capture chip hydrophilic and usable for capturing oil-in-water droplets.

[0083] Ultraviolet / Ozone Treatment: The droplet capture chip bonded in Example 2 is placed in the sample chamber of the ultraviolet / ozone device. After running the device program, water is injected into the chip channel to make the droplet capture chip hydrophilic and usable for capturing oil-in-water droplets.

[0084] Silane coupling agent treatment: Trimethyl[3-(2-methoxy)propyl]silane, a silane coupling agent, is injected into the chip channel treated with oxygen plasma. After reacting in the dark for a period of time, the droplet capture chip becomes hydrophilic and can be used to capture oil-in-water droplets.

[0085] Physically coated hydrophilic layer: The droplet capture chip bonded in Example 2 is placed in a plasma cleaner, and a gas (one or more of oxygen, argon, or nitrogen) is introduced. After running the plasma cleaning program, a hydrophilic solution is injected into the chip channel. After a period of time, excess hydrophilic solution in the channel is flushed away, thus making the droplet capture chip hydrophilic and usable for capturing oil-in-water droplets. The reagents coated in the physically coated hydrophilic layer include one or more of PVA (polyvinyl alcohol), PEG (polyethylene glycol), chitosan, and polydopamine.

[0086] According to the embodiments of this application, the following beneficial effects are achieved:

[0087] By modifying the chip with hydrophobic and hydrophilic methods, the surface properties of the chip can be flexibly adjusted according to the type of droplets captured (water-in-oil or oil-in-water droplets). Hydrophobic modification makes the chip suitable for capturing water-in-oil droplets, while hydrophilic modification is suitable for capturing oil-in-water droplets, greatly expanding the application range of the chip. At the same time, stable hydrophobic or hydrophilic modification methods can ensure that the chip performance is not affected during multiple capture and release processes, improving the reproducibility and reliability of experiments.

[0088] Example 4: Figure 3As shown, this embodiment provides an implementation scheme for a droplet-capturing microfluidic chip in capturing / releasing water-in-oil droplets, as detailed below:

[0089] (1) Preparation and capture of water-in-oil droplets

[0090] By dissolving an emulsifier in oil as a continuous phase and using a saturated calcium chloride solution as a dispersed phase, W / O droplets of suitable size are prepared on a droplet generation microfluidic chip. The droplets are then transported into the chip from any port of the droplet capture microfluidic chip through a channel. When the droplets flow through the microfluidic channel unit, they will fall into the droplet capture microstructure under the action of gravity, thus achieving droplet capture.

[0091] (2) Water-in-oil droplet release scheme

[0092] Invert the chip, keeping the droplet-capturing microstructure on the upper side of the flow channel. Due to gravity, the captured droplets will fall out of the microstructure and distribute themselves within the chip's flow channel. Then, by injecting a solution into the flow channel to flush it, the captured droplets will flow out of the chip, thus releasing them. Simultaneously, after cleaning the chip's flow channel with a detergent and drying any remaining moisture, the chip can be reused.

[0093] (3) Experimental results

[0094] like Figure 3 As shown in (A), when no droplets are captured, the droplet capturing units are neatly arranged within the chip channel. When a droplet is captured, it will fall into the droplet capturing unit. Figure 3 (B)). Once the droplet is released, the chip microstructure will no longer contain the droplet. Figure 3 (C) in the middle). Compare Figure 3 From (A) and (B) in the table and Table 1 below (data on water-in-oil droplet capture, with all data expressed as mean and standard deviation), it can be seen that the chip successfully captured the droplets, achieving a droplet capture rate of up to 75%. (Comparison) Figure 2 As shown in (B) and (C) and Table 1 (data on water-in-oil droplet capture), the droplets captured inside the chip were successfully released, with a droplet release rate of 100%.

[0095] Table 1

[0096]

[0097] In summary, according to this embodiment, the microfluidic chip successfully captures and releases water-in-oil droplets, and the chip can be reused after the droplets are released.

[0098] Example 5: This example provides a specific solution for the application of a microfluidic chip based on droplet capture in in-situ observation of water-in-oil droplets, as detailed below:

[0099] in, Figure 4 (A) in the figure: the state of the droplet captured at 0 min; Figure 4 (B) The state of the droplets captured at 20 min; Figure 4 The state of the droplets captured at (C) 40 min; Figure 4 The state of the droplets captured at (D) 60 min; Figure 4 The state of the droplets captured at (E) 80 min; Figure 4 (F) The droplets captured at 100 min; Figure 4 The variation of the number of droplets captured by (G) in the range of 0-100 min; Figure 4 The particle size change of the droplets captured by (H) in the range of 0-100 min.

[0100] (1) Preparation, capture and in-situ observation of water-in-oil droplets

[0101] Due to factors such as gravity or materials, when observing droplets using substrates or plastic perforated plates, the droplets often shift, deform, or break directly, affecting the observation results and making it difficult to achieve accurate in-situ observation of the droplets. However, when using the droplet capture chip of this invention, since PDMS is an inert material, it avoids direct reaction with the droplets. At the same time, the microstructures distributed in the array within the chip prevent the droplets from shifting, enabling in-situ observation of the droplets.

[0102] Based on this, this experiment will prepare droplets in accordance with the method of Example 4, capture the droplets and photograph the state of the droplets under the same field of view at a fixed position under a microscope at different time periods, and analyze the number of droplets captured and the changes in particle size under that field of view.

[0103] (2) Experimental results

[0104] like Figure 4 As shown in (A)-(F), the droplets captured under the same field of view remained stable within the chip capture unit from 0 to 100 min. The number of droplets captured did not change significantly from 0 to 100 min. Figure 4 According to (G) in Table 2 below (in-situ observation results after water-in-oil droplet capture), the particle size of the captured droplets did not change significantly within 0-100 min. Figure 4 (H) and Table 2 below).

[0105] Table 2

[0106]

[0107] Note: ns: p>0.05 compared to the 0min group. All data are expressed as mean and standard deviation.

[0108] Furthermore, the oil includes corn oil, olive oil, soybean oil, peanut oil, rapeseed oil, sunflower seed oil, flaxseed oil, grapeseed oil, sesame oil, salad oil, blended oil, fish oil, algae oil, and white oil, and may be one or more of these.

[0109] Furthermore, the emulsifier includes, but is not limited to, one or more of the following: soybean lecithin, Span20, Span40, Span60, Span80, Span85, monoglyceride fatty acid glycerides, diglyceride fatty acid glycerides, citrate fatty acid glycerides, lactate fatty acid glycerides, polyglycerol ricinoleate (PGPR), sucrose fatty acid esters, xylitol anhydride monostearate, polyglycerol fatty acid esters, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene stearate, polyoxyethylene stearamide, and polyoxyethylene stearate.

[0110] In summary, the chip provided by this invention successfully achieves the capture and in-situ observation of water-in-oil droplets.

[0111] Example 6: This example provides an implementation scheme for a droplet capture chip in capturing / releasing oil-in-water droplets, as detailed below:

[0112] like Figure 5 As shown, Figure 5 (A): Micrograph of the chip when it is unloaded; Figure 5 (B) in the image: Microscopic image of the chip after it captures the droplet; Figure 5 (C): Microscopic image of the chip after the droplets are released.

[0113] (1) Preparation and capture of oil-in-water droplets

[0114] Polyvinyl alcohol was dissolved in water to prepare a 2% (w / v) solution, which was used as the continuous phase. Polycaprolactone was dissolved in dimethyl carbonate solution to prepare a 3% (w / v) solution, which was used as the dispersed phase. O / W droplets of suitable size were prepared on a droplet generation microfluidic chip. The droplets were then transported into the droplet capture microfluidic chip (hydrophilically modified) through a channel from any port of the chip. As the droplets flowed through the microfluidic channel unit, they fell into the droplet capture microstructure under the influence of gravity, thus achieving droplet capture.

[0115] (2) Water-in-oil droplet release scheme

[0116] Invert the chip, keeping the droplet-capturing microstructure on the upper side of the flow channel. Due to gravity, the captured droplets will fall out of the microstructure and distribute themselves in the chip's flow channel. Then, by injecting an aqueous solution into the flow channel to flush it, the captured droplets will be flushed out of the chip, thus releasing them. Furthermore, by cleaning the chip's flow channel with pure water, the chip can be reused.

[0117] (3) Experimental results

[0118] like Figure 5 As shown in (A), when no droplets are captured, the droplet capturing units are neatly arranged within the chip channel, and there are no foreign objects in the channel. When a droplet is captured, it will fall into the droplet capturing unit. Figure 5 (B)). Once the droplet is released, the chip microstructure will no longer contain the droplet. Figure 5 (C) in the middle). Compare Figure 5 As shown in (A) and (B) and Table 3 below (data on oil-in-water droplet capture), the chip successfully captured oil-in-water droplets, achieving a droplet capture rate of 91.7%. (Comparison) Figure 5 As shown in (B) and (C) and Table 3 below, the droplets captured inside the chip were successfully released, with a droplet release rate of 100%.

[0119] Table 3

[0120]

[0121] Note: All data are expressed as mean and standard deviation.

[0122] Furthermore, the oil phase used in the oil-in-water droplet includes dimethyl carbonate, dichloromethane, ethyl acetate, etc., and may be one or more of these.

[0123] Furthermore, the emulsifier used in the oil-in-water droplets includes polyvinyl alcohol, Tween 80, Tween 20, sodium dodecylbenzene sulfonate, etc., and may be one or more of these.

[0124] Furthermore, the oil phase solute used in the oil-in-water droplets includes polycaprolactone, polylactic acid, polylactic acid-glycolic acid copolymer, etc., and may be one or more of these.

[0125] In summary, the chip provided by this invention successfully captures and releases water-in-oil droplets, and the chip can be reused after the droplets are released.

[0126] Example 7: Figure 6 As shown in the figure, this embodiment provides the application of a microfluidic chip based on droplet capture in in-situ observation of water-in-oil droplets, as detailed below:

[0127] like Figure 6 , Figure 6 (A) in the figure: the state of the droplet captured at 0 min; Figure 6 (B) in the figure: the state of the droplet captured at 2 min; Figure 6 (C) in the figure: the size change of the captured droplets within 0-2 minutes.

[0128] Polymer microspheres are a general term for a class of polymeric material systems widely used in the medical aesthetics industry. Emulsification technology using a single-solvent evaporation system is the main method for preparing polymer microspheres. This involves dissolving the starting material in a volatile solvent, then dispersing it in another solvent immiscible with the first solvent to form oil-in-water droplets. The polymer microspheres are obtained by evaporating the dispersed solvent of the droplets. However, the significant size changes of the droplets and microspheres after solvent evaporation pose a challenge to the industrial production of microspheres with specified particle sizes. Therefore, this embodiment provides an application of droplet capture chips in in-situ observation of oil-in-water droplets, which will help obtain information on the size changes of the microspheres. The specific experimental scheme is as follows:

[0129] (1) Preparation, capture and in-situ observation of oil-in-water droplets

[0130] Polyvinyl alcohol (PVA) was dissolved in water to prepare a 2% (w / v) solution, which was used as the continuous phase. The polymer was dissolved in dimethyl carbonate (DMC) solution to prepare a 3% (w / v) solution, which was used as the dispersed phase. O / W droplets of suitable size were prepared on a droplet generation microfluidic chip. The droplets were then transported into the droplet-capturing microfluidic chip (hydrophilically modified) through a conduit. As the droplets flowed through the microfluidic channel unit, they fell into the droplet-capturing microstructure under gravity, thus achieving droplet capture. With prolonged observation, the DMC in the droplets gradually evaporated, and the droplets eventually transformed into polymer microspheres.

[0131] After capturing the droplets, the state of the droplets was photographed under a microscope at a fixed position at different time periods in the same field of view, and the droplet size change information in the field of view was analyzed.

[0132] (2) Experimental results

[0133] like Figure 6 As shown in (A), polymer water-in-oil droplets are captured by the chip, with an average of 3 droplets captured per channel. The droplets are colorless. Figure 6 As shown in (B), when dimethyl carbonate evaporates, polymer microspheres form and appear black. This phenomenon indicates that the droplet capture chip has successfully recorded the entire process of polymer microsphere transformation from droplets to microspheres. Figure 6 (A) and (B) in the text.

[0134] Further analysis of particle size reveals ( Figure 6 (C) and Table 4 below (in-situ observation results after water-in-oil droplet capture)) The average particle size of polymer microspheres in the state of water-in-oil droplets is 35.6, and the particle size after forming microspheres is 16.2, with a shrinkage rate of 54.53%. That is, compared with water-in-oil droplets, the particle size of polymer microspheres is significantly reduced.

[0135] Table 4

[0136]

[0137] Note: ns: p>0.05 compared to the 0min group; p<0.001 compared to the 0min group. All data are expressed as mean and standard deviation.

[0138] Furthermore, the polymer includes polycaprolactone, polylactic acid, polylactic acid-glycolic acid copolymer, etc., and may be one or more of them.

[0139] In summary, the chip provided by this invention successfully captures water-in-oil droplets and conducts in-situ observation of polymer microspheres, and successfully obtains information on the shrinkage rate of droplets to microspheres, which will provide data support for the industrial production of microspheres with specified particle sizes.

[0140] Based on the above embodiments, this disclosure achieves the following technical effects:

[0141] 1. The present invention features a patterned microstructure chip design, which is simple in structure and allows for arbitrary adjustment of the microstructure size within the chip, enabling the capture of droplets of any size.

[0142] 2. This invention, based on a patterned droplet capture array, enables high-throughput continuous droplet capture and release;

[0143] 3. This invention is based on patterned microstructure chip design, and the microstructure can be customized, which reduces the design difficulty of the chip and makes it easy to mass-produce personalized chips.

[0144] The acquisition, storage, and application of user personal information involved in the technical solution of this application all comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0145] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this application can be achieved, and this is not limited herein.

[0146] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A microfluidic chip based on gravity-captured droplets, characterized in that, The microfluidic chip includes: Microfluidic chip body (6); The microchannel (5) is located inside the microfluidic chip body (6), and the two ends of the microchannel (5) are respectively connected to the chip channel inlet or outlet (2), which is used for the inflow and outflow of droplets; Droplet capturing unit (3), wherein the droplet capturing unit (3) is a circular tunnel unit arrayed in the microchannel (5) for capturing droplets under the action of gravity; Microfluidic chip cover plate (4), the microfluidic chip cover plate (4) covers the microfluidic chip body (6) and fits tightly with the microfluidic chip body (6) together to form a closed microchannel space; The microchannel (5) and droplet capturing unit (3) are either hydrophilic or hydrophobic. The surface properties and structural size of the microchannels and droplet capturing units can be customized according to the properties and size of the droplets. When the chip microchannels and droplet capturing units are hydrophilic, they can capture oil-in-water droplets or multiple droplets with an outermost aqueous solution. When the chip microchannels and droplet capture units are hydrophobic, it is possible to capture water-in-oil droplets or multiple droplets whose outermost layer is an organic solution.

2. The microfluidic chip based on gravity-captured droplets according to claim 1, characterized in that, The chip is made of one or more of the following categories: Polymer materials include polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), polydimethylsiloxane-vinylsiloxane copolymer, polycarbonate (PC), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polypropylene (PP), polyimide (PI), thermoplastic polyurethane (TPU), cyclic olefin copolymer (COC), polystyrene (PS), polyetheretherketone (PEEK), or hydrogels; Inorganic materials: including glass, metals, ceramics, or their surface-functionalized modified materials; Composite materials: including polymer-based nanocomposites, paper-based materials, 3D printing materials, or metal-polymer laminates.

3. The microfluidic chip based on gravity-captured droplets according to claim 1, characterized in that, The microfluidic chip also includes a substrate located at the bottom of the microfluidic chip to support the entire chip.

4. The microfluidic chip based on gravity-captured droplets according to claim 1, characterized in that, The hydrophobicity of the chip can be obtained through hydrophobic modification. The hydrophobic modification is that the molecular structure of the hydrophobic modifier includes groups that can chemically react with the substrate surface and groups that provide hydrophobic properties. The hydrophobic modifier is formed by treating one or more silane reagents and fluorinated reagents. The silane includes one or more of fluorinated silanes, long-chain alkyl silanes, and functionalized silanes; the fluorinated silane is a C3~C-chain perfluorinated alkyl chain. 18 Silanes; long-chain alkylsilanes are C-containing 12 ~C 18 Silanes with alkyl chains; functionalized silanes are silanes containing amino, epoxy, or thiol active groups; fluorinating agents include one or more of fluorocarbons, fluorinated polymers, and fluoride ions.

5. The microfluidic chip based on gravity-captured droplets according to claim 1, characterized in that, Methods for making chips hydrophilic include one or more of plasma treatment, ultraviolet / ozone treatment, silane coupling agent treatment, and physical coating of hydrophilic layers. The gases used in the plasma treatment include one or more of oxygen, argon and nitrogen, and the silane coupling agent used in the silane coupling agent treatment is trimethyl[3-(2-methoxy)propyl]silane. The reagents coated in the physical coating hydrophilic layer include one or more of polyvinyl alcohol, polyethylene glycol, chitosan, and polydopamine.

6. The microfluidic chip based on gravity-captured droplets according to claim 5, characterized in that, The microfluidic chip also has multi-scale capture capabilities, and its targets include: fluid substances, solid / semi-solid materials and other micro / nano-scale functional units. Among them, fluid substances include water-in-oil, oil-in-water monoemulsion droplets and their multiple emulsion droplets; solid / semi-solid materials include microgel particles, polymer microspheres, and inorganic / organic nanoparticles.

7. A method for capturing droplets, characterized in that, The microfluidic chip based on gravity-captured droplets as described in any one of claims 1-6 is used, wherein the droplets are water-in-oil droplets, oil-in-water droplets, or other multiple droplets that will sink under the action of gravity.

8. A method for releasing droplets, characterized in that, The microfluidic chip based on gravity-captured droplets as described in any one of claims 1-6 is used, wherein the droplets are water-in-oil droplets, oil-in-water droplets, or other multiple droplets that will sink under the action of gravity.

9. A method for in-situ observation of droplets, characterized in that, Using the microfluidic chip based on gravity-captured droplets as described in any one of claims 1-6, in-situ observation of water-in-oil droplets or oil-in-water droplets can be performed.

10. The application of the microfluidic chip based on gravity-captured droplets as described in any one of claims 1-6, characterized in that, It is applied to the research and development of droplets and microgels in fields including food, pharmaceuticals, health products, basic scientific research, and life sciences, as well as in the fields of droplet microreactions and microdetection.

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