Coaxial flow droplet micro-fluidic chip based on micro-nano 3D printing

Abstract

The invention relates to the technical field of micro-fluidic chips, and particularly discloses a coaxial flow liquid drop micro-fluidic chip based on micro-nano 3D printing, the coaxial flow liquid drop micro-fluidic chip comprises a sample introduction channel, a sample channel assembly and a gas channel assembly, the sample channel assembly is inserted into the gas channel assembly through a positioning unit with specific geometric characteristics, and the gas channel assembly is inserted into the sample introduction channel. A mechanical interlocking structure is utilized to ensure that a sample channel and a gas channel are kept in high-precision coaxial alignment at the junction, auxiliary adjustment of a microscope is not needed, sample fluid and gas form coaxial laminar flow at the junction of the channels, and liquid drops are generated at an outlet through shearing by controlling the flow rate ratio. According to the invention, the special amphiphilic surface characteristic of a photosensitive resin material is utilized, an airflow shearing mechanism is matched, the high-monodispersity preparation of oil-in-water, water-in-oil and water-in-water single emulsions can be realized in the same chip without carrying out hydrophilic and hydrophobic modification treatment on the surface of a channel, and through parallel design and multi-material printing, the high-monodispersity preparation of the oil-in-water, water-in-oil and water-in-water single emulsions can be realized. The chip can also realize high-throughput production and liquid drop preparation.

Description

Technical Field

[0001] This invention relates to the field of microfluidic chip technology, specifically to a coaxial flow droplet microfluidic chip based on micro / nano 3D printing. Background Technology

[0002] In the biopharmaceutical, new material synthesis, and fine chemical industries, micro- and nano-scale monodisperse droplets play a crucial role, widely used as drug delivery carriers, microreactors, or template microspheres. However, traditional large-scale emulsification techniques (such as high-speed stirring) suffer from safety, efficiency, and stability issues, including uneven droplet size distribution (high polydispersity), high reagent consumption, and difficulty in precisely controlling the microstructure. Therefore, microfluidic technologies are needed to improve these processes. Microfluidics can precisely manipulate tiny volumes of fluid to generate highly monodisperse droplets, but its industrial application has been limited by the complexity and throughput bottlenecks of chip manufacturing.

[0003] Existing technologies, such as traditional glass capillary microfluidic devices, are characterized by the use of nested circular and square glass tubes to construct a coaxial flow focusing structure. While offering advantages like strong chemical resistance and stable droplet generation, they also have significant drawbacks. The assembly of glass capillaries is highly dependent on manual skill, requiring micron-level alignment under a microscope. Even slight deviations can lead to jet eccentricity, affecting droplet quality. Furthermore, once encapsulated, the glass tubes are difficult to replace or adjust, hindering large-scale parallel integration. In addition, while PDMS (polydimethylsiloxane) chips are relatively easy to fabricate, their inherent hydrophobicity necessitates complex surface hydrophilic modification during the preparation of oil-in-water emulsions. This modification is often time-sensitive, resulting in short chip lifespan and poor stability.

[0004] Existing solutions have several drawbacks, including: complex manufacturing and assembly processes, difficulty in ensuring coaxiality leading to low yield rates; limited surface properties of chip materials restricting their versatility in different polarity systems, making it impossible to flexibly prepare W / O and O / W emulsions on the same chip; extremely low single-channel chip throughput, making it difficult to meet the needs of industrial production, while simple multi-channel parallel connections often result in decreased droplet uniformity due to uneven flow resistance distribution. These drawbacks correspond to the problems that this invention addresses. This invention aims to provide a universal microfluidic chip that requires no surface modification, features automatic alignment, and can be produced in high-throughput batches. Summary of the Invention

[0005] This invention provides a coaxial flow droplet microfluidic chip based on micro / nano 3D printing, aiming to solve the problem that the multi-channel parallel connection of microfluidic chips in related technologies often results in low droplet uniformity due to uneven flow resistance distribution.

[0006] A coaxial flow droplet microfluidic chip based on micro / nano 3D printing includes: a chip body, wherein at least one droplet generating unit is integrated inside the chip body; the droplet generating unit is designed based on a coaxial flow structure and mainly includes a sample inlet channel, a sample channel assembly, and a gas channel assembly; the sample inlet channel is connected to the sample channel assembly to form a sample flow channel for continuous sample addition; the outer wall of the sample channel assembly is provided with a positioning unit, and the sample channel assembly is inserted into and fixed to the internal cavity of the gas channel assembly through the positioning unit, such that the sample channel at the front end of the sample channel assembly is located on the central axis of the gas channel inside the gas channel assembly, and the sample channel and the gas channel are coaxially aligned at the confluence; the chip body is printed using photosensitive resin material using micro / nano 3D printing technology; the outlet of the sample channel is aligned with the outlet of the gas channel or has a preset axial distance, the sample fluid and gas converge at the outlet and are ejected into a collection pool below under the shearing action of the airflow.

[0007] The advantages are as follows: This invention utilizes the mechanical cooperation between the positioning unit and the internal cavity of the gas channel assembly to achieve micron-level self-alignment assembly. Compared to traditional glass capillaries that rely on manual microscope alignment, this invention significantly reduces assembly difficulty and ensures the axisymmetry of the flow field, thereby generating highly monodisperse droplets. Simultaneously, the airflow shearing mechanism combined with the amphiphilicity of the 3D printing material ensures that the dispersed phase is cut off by the high-speed airflow before wetting forces dominate at the contact wall surface. Therefore, various types of emulsions can be prepared universally without any chemical modification of the channel surface.

[0008] Preferably, the sample channel in the sample channel assembly is designed as a tapered structure that gradually narrows along the fluid flow direction; the positioning unit is a square boss structure located at the rear end of the sample channel, with a side length of 4-8 mm and a thickness of 1-3 mm; the gas channel assembly has a positioning groove inside that matches the square boss structure, achieving radial limiting and anti-rotation through the fit of the square cross-section; the main body length of the sample channel is 10-20 mm, and the inner diameter of the end sample outlet is 200-400 μm, and the outer diameter is 800-1500 μm. Using the above structure, the square boss positioning unit not only provides an axial positioning reference but also provides an anti-rotation function through its non-circular geometric features, ensuring that the sample channel will not experience angular displacement during assembly. The tapered sample channel 7 facilitates fluid rectification and acceleration, reduces dead volume, and, combined with the micron-level end outlet size, enables precise control of droplet generation size.

[0009] Preferably, the gas channel in the gas channel assembly surrounds the sample channel, with a main body length of 15-25 mm and an inner diameter of 1000-2500 μm at the outlet. The sample inlet channel is a circular hollow pipe with a main body length of 5-15 mm, an inner diameter of 2-5 mm, and an outer diameter of 5-10 mm. The gas channel assembly also has a gas inlet connected to the gas channel. With this structure, specific dimensional ratios, such as the optimized ratio of the inner diameter of the sample outlet to the gas outlet, ensure smooth airflow while creating a sufficiently high Weber number We at the nozzle, enhancing the shearing effect. The larger inner diameter of the gas channel prevents insufficient flow velocity at low pressures and also avoids the risk of blockage due to an excessively narrow channel.

[0010] Preferably, the photosensitive resin material used in the chip body has amphiphilic surface properties, with a contact angle of 40°-50° in an aqueous environment and 40°-50° in an oil environment after curing. Utilizing this contact angle range and the low viscosity of the gas continuous phase, the dispersed phase fluid is sheared and separated by the gas flow before a stable wetting film is formed, thus enabling the preparation of oil-in-water or water-in-oil emulsions without surface modification. This structure overcomes the limitation of traditional microfluidic chip materials such as hydrophobic PDMS and hydrophilic glass, which can only prepare specific types of emulsions. The 40°-50° contact angle is in the middle range of wettability, and combined with the low viscosity and high flow rate of the gas, the droplet formation process is mainly controlled by inertial and shear forces, rather than surface tension-dominated wetting, significantly improving the chip's versatility and durability.

[0011] Preferably, the chip body adopts a parallel integrated design, including at least one droplet generating unit connected in parallel; all units share a high-throughput sample inlet and a high-throughput gas inlet; the high-throughput sample inlet is connected to the sample inlet channel of each unit through an internal fluid distribution network, and the high-throughput gas inlet is connected to the gas channel of each unit through an internal gas distribution network, and the dimensional parameters of each unit are consistent. Using the above structure, by integrating multiple independent droplet generating units into the same chip body, and utilizing the freeform molding capability of 3D printing to construct complex internal flow paths, high-throughput droplet production is achieved. The shared inlet design simplifies external pipeline connections, making operation more convenient.

[0012] Preferably, the parallel integrated design includes several parallel droplet generating units; the internal fluid distribution network adopts a hierarchical and branching structure to ensure equal flow resistance from the high-throughput sample inlet to the outlet of each sample channel, thereby enabling each unit to simultaneously and stably generate uniform microdroplets. This structure further clarifies the array design of the channels. The equal flow resistance distribution network, such as a fractal tree structure, ensures consistent pressure and velocity of the fluid reaching each nozzle, thus overcoming the common problem of uneven flow distribution in parallel microfluidic systems and ensuring the overall monodispersity of the product.

[0013] Preferably, the droplet generating unit is further configured to prepare core-shell structured droplets. The sample channel assembly contains an inner fluid channel, forming a three-phase flow coaxial structure. The inner fluid channel, sample channel, and gas channel are sequentially coaxially nested to generate a dual emulsion during a single shearing process. This structure expands the chip's functional applications. Utilizing the same coaxial self-alignment principle, multi-layered sleeve structures can be constructed to achieve one-step preparation of complex dual emulsions (such as W / O / W), demonstrating the excellent scalability of this technology platform.

[0014] Preferably, the droplet generating unit is further configured to prepare Janus droplets, and the sample channel assembly includes two parallel sub-channels that converge at their ends. The two sub-channels are respectively supplied with fluids of different properties and are sheared together by the gas flow at the outlet of the gas channel. Using the above structure, the ability to construct non-axisymmetric or parallel flow channels through 3D printing enables the preparation of anisotropic particles, enriching the product forms of microfluidic chips.

[0015] Preferably, the micro / nano 3D printing technology is projection micro-stereolithography, with a printing layer thickness set to 10-50 μm and an XY plane resolution better than 25 μm, to ensure the roundness of the nozzle at the end of the sample channel and the smoothness of the inner wall. Using the above structure, the manufacturing process parameters are clearly defined. High-precision PμSL technology is fundamental to realizing micron-level complex internal cavity structures (especially suspended coaxial structures) and low-roughness surfaces, directly affecting the fluid flow state and the stability of droplet formation.

[0016] Preferably, a method for preparing microdroplets using the above-mentioned chip involves introducing a dispersed phase fluid into a sample inlet channel and introducing a continuous phase gas into a gas channel assembly. The gas-liquid flow rate ratio is adjusted, and the shear force and pressure difference generated by the high-speed gas flow at the gas channel outlet are used to shear the dispersed phase fluid flowing out of the sample outlet into discrete droplets. The droplets fall directly into a collection pool positioned perpendicular to the channel outlet. This method, by replacing traditional liquid-liquid shearing with a gas-liquid shearing mechanism, not only reduces the cost of the continuous phase (gas) but also simplifies subsequent separation and purification steps (eliminating waste oil treatment). The vertical collection method avoids droplet fusion or breakage during pipeline transportation.

[0017] By adopting the above technical solution, the beneficial effects of the present invention are as follows: This invention utilizes micro-nano 3D printing technology to design a unique structure that combines a positioning unit with a gas channel component, enabling modular, high-precision self-aligned assembly of microfluidic chips. This completely solves the problems of difficult alignment and poor consistency in traditional glass capillary chips, significantly improving manufacturing efficiency and yield.

[0018] This invention utilizes the amphiphilic surface properties of photosensitive resin materials in the 40°-50° range, combined with an airflow shearing mechanism, to break the strict requirements of traditional chips on surface wettability. Water-in-oil, oil-in-water, and water-in-water emulsions can be prepared in the same chip without any physical or chemical modification, significantly reducing the cost and complexity of use.

[0019] 3. This invention integrates five parallel units within a single chip through parallel integrated design. Combined with an equal flow resistance fluid distribution network, it successfully solves the bottleneck of low yield in microfluidic technology, achieving a significant increase in droplet yield while maintaining high monodispersity, and has the potential for industrial application. Attached Figure Description

[0020] Figure 1 This is a component diagram of the gas shear coaxial flow droplet microfluidic chip for single droplet generation according to the present invention.

[0021] Figure 2 This is a schematic diagram illustrating the fabrication and droplet collection of the gas shear coaxial flow droplet microfluidic chip of the present invention.

[0022] Figure 3 This is a schematic diagram of the gas shear microfluidic chip for high-throughput multi-droplet generation according to the present invention.

[0023] Figure 4 This is a micrograph of a droplet prepared using the chip of the present invention.

[0024] Reference numerals: 1. Sample inlet tube; 2. Inner channel; 3. Outer coaxial assembly; 4. Sample inlet; 5. Positioning unit; 6. Gas inlet; 7. Sample channel; 8. Gas channel; 9. Sample outlet; 10. Gas outlet; 11. Collection cell; 12. High-throughput sample inlet; 13. High-throughput gas inlet. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] like Figures 1-4As shown, a coaxial flow droplet microfluidic chip based on micro / nano 3D printing is disclosed. The chip system mainly consists of sample channel component A (corresponding to sample channel component 2 and related components), gas channel component B (corresponding to gas channel component 3 and related components), and high-throughput fluid system C (corresponding to the high-throughput embodiment). The general process is as follows: components with self-alignment features are manufactured separately or integrally using high-precision projection micro-stereolithography technology, and then assembled to form a coaxial flow channel; the dispersed phase liquid and continuous phase gas are introduced into the chip, and droplets are formed by airflow shearing at the nozzle, and finally collected.

[0027] Sample channel assembly A is the core internal phase component for droplet generation, and its structural design focuses on fluid rectification and precision delivery. A includes a sample inlet channel 1, a positioning unit 5, a sample channel 7, and a sample outlet 9. The sample inlet channel 1 is located at the rear end of the assembly and is designed as a cylindrical hollow pipe for connecting to an external injection pump.

[0028] In Example 1, the main body length of sample inlet channel 1 is 5-15 mm, the inner diameter is designed to be 2-5 mm, and the outer diameter is 5-10 mm. This size design ensures compatibility with standard laboratory tubing and provides sufficient mechanical strength for handheld or clamp fixation. The positioning unit 5 is a key structure for achieving high-precision self-assembly in this invention, located between sample inlet channel 1 and sample channel 7.

[0029] The positioning unit 5 is designed as a boss with a polygonal cross-section, preferably a square boss positioning unit. The side length of this square boss is set to 4-8 mm, and the thickness is 1-3 mm. The positioning unit 5 has a dual function: firstly, it acts as a mechanical limiter, precisely controlling the insertion depth of the sample channel assembly 2 into the gas channel assembly 3, thereby ensuring the accuracy of the axial Z-axis position; secondly, the square geometry provides strict radial XY plane constraints and anti-rotation function. Compared with traditional circular positioning, the square structure can effectively prevent the inner channel from rotating under assembly or fluid impact, ensuring that the nozzle is always in the optimal flow field position.

[0030] The sample channel 7 is connected to the front end of the positioning unit 5 and has a tapered structure that gradually narrows along the fluid flow direction. The main body length of the sample channel 7 is 10-20 mm. Its internal flow channel adopts a streamlined contraction design, which can stabilize the fluid flow rate and eliminate turbulence. The sample outlet 9 is located at the very end of the sample channel 7 and is the specific location for droplet generation. The inner diameter of the sample outlet 9 is precisely manufactured to be 200-400 μm, and the outer diameter is 800-1500 μm. To reduce the wake effect, the wall thickness of the sample outlet 9 is designed to be as thin as possible at the end. This tiny dimension is achieved using projection micro-stereolithography technology with an XY plane resolution better than 25 μm, ensuring the high roundness of the nozzle cross-section.

[0031] Gas channel assembly B, serving as a channel and mounting base for the external phase fluid, is enclosed on the outside of sample channel assembly A. B includes a positioning groove located inside the assembly, a gas inlet 6, a gas channel 8, and a gas outlet 10. The positioning groove is located inside the rear end of gas channel assembly 3, and its shape and size fit tightly with the square boss of positioning unit 5.

[0032] When sample channel assembly 2 is inserted, positioning unit 5 engages with positioning slot, achieving automatic alignment. Due to the cooperation between positioning unit 5 and positioning slot, the central axis of sample channel 7 is forced to coincide with the central axis of gas channel 8, eliminating human assembly errors. Gas inlet 6 is located on the side wall of gas channel assembly 3 and communicates with gas channel 8, used to introduce compressed gas such as nitrogen.

[0033] The gas inlet 6 can be designed to be vertical or tangential to reduce airflow turbulence. The gas channel 8 is an annular space surrounding the sample channel 7. The main body length of the gas channel 8 is 15-25 mm, and at the end outlet, the inner diameter of the gas channel 8 narrows to 1000-2500 μm. The sample channel 7 is suspended on the internal central axis of the gas channel 8. The gas outlet 10 is the end opening of the gas channel 8. After assembly, the sample outlet 9 is located inside the gas outlet 10 or flush with its end face. The annular gap formed between the two is a key area for airflow acceleration and shear force generation.

[0034] In Example 2, the present invention demonstrates the application of a high-throughput fluid system C for parallel production. The chip body contains five droplet generating units connected in parallel.

[0035] The high-throughput fluid system C includes a high-throughput sample inlet 12, a high-throughput gas inlet 13, and an internal fluid distribution network. The high-throughput sample inlet 12 and the high-throughput gas inlet 13 replace the independent inlets in single-channel mode. The high-throughput sample inlet 12 is connected to five parallel sample injection channels 1 through the internally integrated fluid distribution network.

[0036] The fluid distribution network is designed according to the principle of equal flow resistance, for example, by using a fractal tree structure to ensure that the path length and flow resistance from the main inlet to each distribution unit are equal. This means that when an external pump supplies a certain flow rate, the sample fluid will be distributed absolutely uniformly into the five sample channels 7.

[0037] The high-throughput gas inlet 13 is also connected to five parallel gas channels 8 via internal gas flow branching. Due to the compressibility of gas, the gas distribution network is typically designed with a large buffer cavity (Plenum) to balance the pressure in each branch and ensure consistent airflow velocity at the five nozzles. This design allows the five units to operate simultaneously while maintaining a high degree of uniformity in the size of the generated droplets, thereby increasing droplet production by five times without increasing operational complexity.

[0038] Working principle: In use, the user first inserts the sample channel assembly 2 into the gas channel assembly 3 via the positioning unit 5 to complete chip assembly. Due to the precise fit between the square structure of the positioning unit 5 and the positioning groove, the sample outlet 9 is automatically and accurately positioned at the geometric center of the gas outlet 10 without any subsequent adjustments. The liquid dispersion phase of the sample to be dispersed is pumped into the sample inlet channel 1, filling the sample channel 7 and reaching the sample outlet 9. Simultaneously, a continuous gas phase with a certain pressure is introduced into the gas inlet 6, where the gas flows and accelerates in the gas channel 8. Since the outer diameter of the sample outlet 9 (800-1500 μm) is smaller than the inner diameter of the gas outlet 10 (1000-2500 μm), an annular airflow channel is formed between them. The high-speed airflow generates strong viscous shear force and Bernoulli negative pressure here.

[0039] When the sample fluid flows out from the sample outlet 9, it is stretched, thinned, and cut into microdroplets by the high-speed airflow before it can spread and wet the nozzle end face. The droplets are ejected from the chip by the airflow and fall into the collection pool 11 below. Because the photosensitive resin material used in this invention has an amphiphilic water contact angle of 40-50° and an oil contact angle of 40-50°, the wettability on the nozzle surface is in an intermediate state, regardless of whether the dispersed phase is water or oil. It is neither completely wetted nor completely repelled. Combined with the rapid shearing of the gas, the fluid cannot form a stable adhesion layer, thus avoiding the "wall sticking" or "jet instability" phenomena commonly found in traditional chips. This allows the same chip to be used to prepare W / O, O / W, or even W / W emulsions without modification.

[0040] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A coaxial flow droplet microfluidic chip based on micro / nano 3D printing, characterized in that, Includes a chip body, wherein at least one droplet generating unit is integrated inside the chip body; The droplet generating unit is designed based on a coaxial flow structure and mainly includes a sample inlet channel (1), a sample channel assembly (2), and a gas channel assembly (3). The sample inlet channel (1) is connected to the sample channel assembly (2) to form a sample flow channel that can continuously add samples. The outer wall of the sample channel assembly (2) is provided with a positioning unit (5). The sample channel assembly (2) is inserted into and fixed to the internal cavity of the gas channel assembly (3) through the positioning unit (5), so that the sample channel (7) at the front end of the sample channel assembly (2) is located on the central axis of the gas channel (8) inside the gas channel assembly (3), and the sample channel (7) and the gas channel (8) are coaxially aligned at the junction. The chip body is printed using photosensitive resin material by micro-nano 3D printing technology; the outlet of the sample channel (7) is aligned with the outlet of the gas channel (8) or has a preset axial distance, the sample fluid and gas converge at the outlet and are sprayed into the collection pool (11) below under the shearing action of the airflow.

2. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The sample channel (7) in the sample channel assembly (2) is designed as a tapered structure that gradually narrows along the fluid flow direction; the positioning unit (5) is a square boss structure set at the rear end of the sample channel (7), the side length of the positioning unit (5) is 4-8mm and the thickness is 1-3mm; the gas channel assembly (3) is provided with a positioning groove that matches the square boss structure, and radial limiting and anti-rotation are achieved through the cooperation of the square cross section; the main body length of the sample channel (7) is 10-20mm, the inner diameter of the end sample outlet (9) is 200-400um and the outer diameter is 800-1500um.

3. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The gas channel (8) in the gas channel assembly (3) is wrapped around the sample channel (7), with a main body length of 15-25 mm and an inner diameter of 1000-2500 μm at the end outlet; the sample injection channel (1) is a circular hollow pipe with a main body length of 5-15 mm, an inner diameter of 2-5 mm, and an outer diameter of 5-10 mm; the gas channel assembly (3) is also provided with a gas inlet (6), which is connected to the gas channel (8).

4. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The photosensitive resin material used in the chip body has amphiphilic surface properties. After curing, its contact angle is 40°-50° in an aqueous environment and 40°-50° in an oil environment. By utilizing this contact angle range and the low viscosity of the gas continuous phase, the dispersed phase fluid is sheared and separated by the airflow before a stable wetting film is formed, thereby preparing water-in-oil or oil-in-water emulsions without surface modification.

5. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The chip body adopts a parallel integrated design and includes at least two droplet generating units connected in parallel. All units share a high-throughput sample inlet (12) and a high-throughput gas inlet (13). The high-throughput sample inlet (12) is connected to the sample injection channel (1) of each unit through an internal fluid distribution network, and the high-throughput gas inlet (13) is connected to the gas channel (8) of each unit through an internal gas distribution network. The size parameters of each unit are consistent.

6. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The parallel integrated design includes five parallel droplet generating units; the internal fluid distribution network adopts a hierarchical and bifurcated structure to ensure that the flow resistance from the high-throughput sample inlet (12) to the outlet of each sample channel (7) is equal, so as to achieve the simultaneous and stable generation of uniform microdroplets by each unit.

7. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The droplet generating unit is also configured to prepare core-shell structured droplets. The sample channel assembly (2) has an inner fluid channel nested inside to form a three-phase flow coaxial structure. The inner fluid channel, sample channel (7) and gas channel (8) are coaxially nested in sequence to generate a double emulsion during a single shearing process.

8. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The droplet generating unit is also configured to prepare Janus droplets. The sample channel assembly (2) includes two parallel sub-channels that converge at their ends. The two sub-channels are respectively introduced into fluids of different properties and are sheared together by the airflow at the outlet of the gas channel (8).

9. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to claim 1, characterized in that, The micro-nano 3D printing technology is projection micro-stereolithography, with the printing layer thickness set to 10-50um and the XY plane resolution better than 25um, in order to ensure the roundness of the nozzle at the end of the sample channel (7) and the smoothness of the inner wall.

10. The coaxial flow droplet microfluidic chip based on micro / nano 3D printing according to any one of claims 1-9, characterized in that, The dispersed phase fluid is introduced into the sample inlet channel (1), and the continuous phase gas is introduced into the gas channel assembly (3). The gas-liquid flow rate ratio is adjusted, and the shear force and pressure difference generated by the high-speed flow of gas at the outlet of the gas channel (8) are used to shear the dispersed phase fluid flowing out of the sample outlet (9) into discrete droplets. The droplets fall directly into the collection pool (11) set perpendicular to the channel outlet.

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