Construction method of micro-spiral flow and precision regulation and prediction method of structural characteristics thereof

Abstract

This invention belongs to the field of microfluidics technology and provides a method for constructing microhelical flows and a method for precisely controlling and predicting their structural characteristics. The method for constructing microhelical flows utilizes a high-viscosity inner phase fluid and a low-viscosity outer phase fluid. By controlling the viscosity ratio and flow rate ratio of the inner and outer phase fluids, and based on the fluid rope effect, a simple and controllable construction of microhelical flows can be achieved. By adjusting operating conditions such as the viscosity of the inner and outer phase fluids, the inner diameter of the injection tube's conical opening, the inner diameter of the receiving tube, and the flow rates of both the inner and outer phase fluids during the construction process, precise control of the microhelical flow's structural characteristics can be achieved. This invention also derives the relationship between the structural characteristics of the microhelical flow and the operating conditions, enabling the prediction of the microhelical flow's structural characteristics. This invention can improve the stability and controllability of the microhelical flow construction process, expand its applicability to different solution systems, and effectively guide the design of microhelical flow preparation process conditions.

Description

Technical Field

[0001] This invention belongs to the field of microfluidics technology, and relates to the construction method of micro-helical flow and the precise control and prediction method of its structural characteristics. Background Technology

[0002] Microhelices, due to their stretchability / compressibility, three-dimensional spatial structure, and helical motion capabilities, are widely used in important fields such as mechanical engineering, materials science, and biomedicine. Based on microfluidic technology, which allows for the flexible construction and control of microhelical flows, researchers have developed microhelices with diverse structures and functions, such as smart sensors, biomimetic robots, and biological soft tissues, all demonstrating excellent application results, attracting increasing attention from researchers. The fluid rope effect is the fundamental principle for constructing microhelical flows in microfluidics; specifically, microfluidics rapidly generate gels through cross-linking reactions in receiving tubes, triggering fluid instability and forming helical structures. In terms of construction systems, the ionic cross-linking method, typically using sodium alginate (NaAlg)-CaCl2, is the main strategy for microhelical flows, efficiently preparing CaAlg microhelices. However, to meet the needs of diverse application scenarios regarding substrates and solutions, such as a wide range of selectable substrate types and safe, compatible solution systems, new requirements are placed on the construction systems of microhelical flows. In terms of structural characteristics, microhelices possess a wealth of parameters, including pitch, diameter, amplitude, length, frequency, and tilt angle, which significantly influence their functional properties. For example, pitch affects the tensile and kinematic properties of the microhelices, enabling them to exhibit excellent thrombectomy effects in minimally invasive treatments. Diameter significantly impacts the mechanical strength of the microhelices, allowing the nanoyarn to exhibit good resistance to deformation. Amplitude primarily determines the spatial dimensions of the microhelices, enabling them to precisely match blood vessel dimensions and exhibit outstanding support. Specifically, by adjusting operating conditions such as solution composition, two-phase flow rate, and microchannel size, the stress balance of microfluidic coil deformation can be coordinated, thereby precisely controlling the structural characteristics of the microhelical flow. Furthermore, to improve the design efficiency of microhelical flow, it is necessary to further establish a detailed control relationship between operating conditions and structural characteristics. Therefore, precisely controlling the structural characteristics of microhelical flow in microfluidic systems is of great significance for the function and application of microhelices.

[0003] Researchers have developed numerous methods to control the structural characteristics of microhelical flows, primarily including solvent evaporation, chemical crosslinking, and physical crosslinking. In the solvent evaporation method, the principle is to form connection points between polymer molecular chains through hydrogen bonds or van der Waals forces, mainly manifested as crystallization or precipitation, thereby increasing the microfluidic viscosity to achieve the construction of microhelices. Liu et al. (Angew. Chem. Int. Ed., 2021, 60, 25089-25096) prepared PCL microhelices in a system of polycaprolactone (PCL) in formic acid (FA) solution and pure water, and controlled the structural characteristics of the PCL microhelices by adjusting the tilt angle of the device. Xing et al. (J. Am. Ceram. Soc., 2017, 100, 4977-4982) prepared YSZ microhelices in a system of yttrium oxide and polyethersulfone in N-methyl-2-pyrrolidone (NMP) solution and pure water. The crosslinking speed of this method is relatively slow, and the deformation process of the helical coil is dominated by weak control forces, resulting in poor helical morphology. In the chemical crosslinking method, the principle is to introduce a crosslinking agent to form covalent bonds between polymer chains, then transform the linear molecular chains of the polymer into a three-dimensional network structure, and finally induce a phase transition to trigger the microfluidic helical coiling. Yang et al. (Macromol. Rapid Commun., 2019, 40, 1900111) controlled the helical morphology of CCS microfluidics in a two-stage receiving tube microfluidic device by adjusting the two-phase solute concentration ratio of carboxylated chitosan (CCS) aqueous solution and polyvinyl alcohol (PVA) aqueous solution to PEG aqueous solution. This method achieves online preparation of microhelices based on the strategy of simultaneous morphology control and substrate crosslinking. It shows poor correlation in the control relationship of structural characteristics and large fluctuations, which is not conducive to predicting structural characteristics. In the physical crosslinking method, the principle is to form ionic or coordinate bonds between polymer molecular chains through chemical reactions to construct a three-dimensional network structure, which promotes the increase of viscosity of the microfluidic during the phase transition to induce helical coiling behavior.In a typical NaAlg-CaCl2 system, Grolman et al. (Adv. Mater., 2015, 27, 5512-5517) constructed hollow CaAlg microspirals with a wavy pattern in a microfluidic device. Tottori et al. (RSC Advances, 2015, 5, 33691-33695) added sodium citrate to the CaCl2 solution in the outer phase to regulate the crosslinking rate of the CaAlg gel and control the morphology of the microspirals. Yu et al. (Adv. Mater., 2017, 29, 1605765) studied the changes in flow states such as jet, spiral, wavy, and clogging by adjusting the operating conditions. Guo et al. (LabChip, 2021, 21, 2594-2604) incorporated the size ratio and flow rate ratio into the regulation of structural characteristics to analyze the comprehensive influence of operating conditions. This system involves interfacial mass transfer and ionic reactions, i.e., Ca in the outer phase. 2+ After diffusing into low-viscosity NaAlg, it then interacts with the -COO groups on its molecular chain. - Electrostatic coordination generates a three-dimensional network structure with rapid reaction kinetics. The deformation process is difficult to decouple, resulting in low controllability of the helical morphology and significant nonlinearity in the control relationship. Furthermore, microfluidics often exhibit wall-attached behavior, and the frictional resistance of the receiving tube's inner wall induces unfavorable deformations such as twisting and tilting of the micro-helical flow, leading to a poor helical morphology and hindering precise control of the target structural features.

[0004] Therefore, how to solve the important problems of insufficient stability, continuity and controllability of the preparation process and limited applicable solution systems in the construction of microhelices and the regulation of microhelical structural characteristics in existing technologies, and thus achieve simple and controllable construction of microhelical flow and precise regulation and prediction of its structural characteristics, still faces great challenges. Summary of the Invention

[0005] To address the shortcomings of existing technologies in constructing and controlling microhelical structures, such as insufficient stability, continuity, and controllability of the preparation process and limited applicability to solution systems, this invention provides a method for constructing microhelical flows and a method for precise control and prediction of their structural characteristics. This method constructs microhelical flows based on viscosity and velocity differences, achieving simple and controllable construction and precise control and prediction of their structural characteristics. It also expands the applicability of the construction method to different solution systems, thereby better guiding the design of microhelical flow preparation process conditions.

[0006] To achieve the aforementioned objectives, the technical concept employed in constructing the micro-spiral flow in this invention primarily involves using a high-viscosity internal phase fluid and a low-viscosity external phase fluid. By controlling the viscosity ratio and flow rate ratio between the internal and external phase fluids, the micro-spiral flow is constructed based on the fluid rope effect. Specifically, the high-viscosity internal phase fluid expands and is extruded at the conical opening of the injection tube, initially forming a coaxial laminar flow with the low-viscosity external phase fluid. Then, under the competitive action of viscous forces, shear forces, and inertial forces, it continuously swirls at an appropriate location due to fluid instability, ultimately forming a stable micro-spiral flow. The construction process of the micro-spiral flow described in this invention does not involve cross-linking reactions or phase transition processes, thereby improving the stability and controllability of the micro-spiral flow forming process.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for constructing a micro-helical flow includes the following steps:

[0009] (1) Prepare internal phase fluid and external phase fluid

[0010] Preparation of internal phase fluid: Dissolve a water-soluble polymer compound in water or glycerol to obtain an internal phase fluid; or dissolve or fully disperse a water-soluble polymer compound, a water-soluble photopolymerizable polymer monomer, and a photoinitiator in water or glycerol to obtain an internal phase fluid;

[0011] Preparation of external phase fluid: Use water as the external phase fluid; or dissolve glycerol in water to obtain the external phase fluid;

[0012] The viscosity of the internal phase fluid is controlled to be 50~1000 mPa·s, and the viscosity of the external phase fluid is controlled to be 1~20 mPa·s; the viscosity ratio of the internal phase fluid to the external phase fluid is controlled to be (50~1000):1.

[0013] (2) Constructing micro-spiral flow

[0014] A micro-spiral flow is constructed using a primary microfluidic device, which includes an injection tube, a receiving tube, and a connecting tube. The outlet of the injection tube is tapered and is inserted into the inlet of the receiving tube. The injection tube and the receiving tube are connected by the connecting tube, and the injection tube, connecting tube, and receiving tube are arranged coaxially. The primary microfluidic device is arranged vertically, with the injection tube above the receiving tube. A receiving container filled with receiving liquid is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container. The receiving liquid is water. The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube respectively using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the conical opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid slows down and forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability, forming a continuous and stable micro-spiral flow in the receiving tube.

[0015] In this step, the ratio of the flow rate of the inner phase fluid to the flow rate of the outer phase fluid is controlled to be (10~150):1.

[0016] In step (1) of the above-mentioned method for constructing microspiral flow, the role of water-soluble polymer compounds is mainly to adjust the viscosity of the internal phase fluid. Any water-soluble polymer compound that can play this role can be used to prepare the internal phase fluid. For example, feasible water-soluble polymer compounds include sodium alginate (NaAlg), polyvinyl alcohol (PVA), chitosan (CS), sodium carboxymethyl cellulose (CMC), or hydroxypropyl methyl cellulose (HPMC). However, feasible water-soluble polymer compounds are not limited to the specific types of polymer compounds listed above. The role of water-soluble photopolymerizable polymer monomers is to solidify the microspiral flow into microspirals after photo-initiated crosslinking. As the matrix material of the microspirals, water-soluble photopolymerizable polymer monomers can be selected according to actual application requirements. For example, feasible water-soluble photopolymerizable polymer monomers include polyethylene glycol dimethacrylate (PEGDA), methacrylic hydrogel (GelMA), or N-isopropylacrylamide (NIPAM). However, feasible water-soluble photopolymerizable polymer monomers are not limited to the specific types of polymer monomers listed above.

[0017] In the above-mentioned method for constructing micro-spiral flow, the internal phase fluid and external phase fluid in step (1) can be replaced simultaneously with the internal phase fluid and external phase fluid prepared by the following method;

[0018] Preparation of internal phase fluid: Use an oil-soluble liquid as the internal phase fluid; or dissolve an oil-soluble photopolymerizable polymer monomer and a photoinitiator in an oil-soluble liquid to obtain an internal phase fluid; or dissolve or fully disperse an oil-soluble photopolymerizable polymer monomer, a photoinitiator, and an oil-soluble liquid in an oil phase solvent to obtain an internal phase fluid;

[0019] Preparation of external phase fluid: using an oil phase solvent as the external phase fluid; or dissolving an oil-soluble liquid in an oil phase solvent to obtain an external phase fluid;

[0020] The viscosity of the oil phase solvent is 1~10 mPa·s; the viscosity of the internal phase fluid is controlled to be 50~1000 mPa·s, and the viscosity of the external phase fluid is controlled to be 1~20 mPa·s; the ratio of the viscosity of the internal phase fluid to the viscosity of the external phase fluid is controlled to be (50~1000):1.

[0021] In the above-mentioned method for constructing microspiral flow, the role of the oil-soluble liquid is mainly to adjust the viscosity of the internal phase fluid. Any oil-soluble liquid that can play this role can be used to prepare the internal phase fluid. For example, feasible oil-soluble liquids include silicone fluid, polydimethylsiloxane (PDMS), or polyglycerol ricinoleate (PGPR). However, feasible oil-soluble liquids are not limited to the specific types of oil-soluble liquids listed above. The role of the oil-soluble photopolymerizable polymer monomer is to solidify the microspiral flow into microspirals after photo-initiated crosslinking. As the matrix material of the microspirals, the oil-soluble photopolymerizable polymer monomer can be selected according to the actual application requirements. For example, feasible oil-soluble photopolymerizable polymer monomers include ethoxylated trimethylolpropane triacrylate (ETPTA) or UV-curable resin. However, feasible oil-soluble photopolymerizable polymer monomers are not limited to the specific types of polymer monomers listed above. The role of an oil phase solvent is to provide a low-viscosity external fluid environment, or to serve as a medium for dissolving oil-soluble photopolymer monomers, oil-soluble photoinitiators, oil-soluble liquids, etc. For example, feasible oil phase solvents include silicone oil, methyl oil, or soybean oil, but feasible oil phase solvents are not limited to the specific types of oil phase solvents listed above.

[0022] In the above-described method for constructing micro-spiral flows, the photoinitiator includes water-soluble or oil-soluble photoinitiators, which should be selected according to actual needs. For example, water-soluble photoinitiators include Irgacure 819, Irgacure 1173, or Irgacure 2959, but feasible water-soluble photoinitiators are not limited to the specific types listed above. Similarly, oil-soluble photoinitiators include azobisisovalerate (AMBN), azoisobutyl cyanoformamide (CABN), or azobiscyclohexylformamide (ACCN), but feasible oil-soluble photoinitiators are not limited to the specific types listed above.

[0023] In step (1) of the above-mentioned method for constructing microspiral flow, in order to facilitate observation during the construction of microspiral flow, when the internal phase fluid is an aqueous system (prepared with water or glycerol as solvent), the internal phase fluid may also contain water-soluble dyes, such as Rhodamine B, Neutral Red, Congo Red, etc.; when the internal phase fluid is an oily system (prepared with oil-soluble liquid or oil phase solvent), the internal phase fluid may also contain oil-soluble dyes, such as Sudan III, Oil Red O, Lumogen Red 300, etc.

[0024] In the above-mentioned technical solution for constructing micro-spiral flow, when the internal phase fluid is an aqueous system, the viscosity of the internal phase fluid can be adjusted by adjusting the concentration of each component in the internal phase fluid. In practical applications, the concentration of each component in the internal phase fluid can be determined according to the requirements for the viscosity of the internal phase fluid. When the internal phase system is an oily system, the viscosity of the internal phase fluid can be adjusted by adjusting the viscosity of the oil-soluble liquid and the concentration of each component in the internal phase fluid. In practical applications, the concentration of each component in the internal phase fluid and the viscosity of the oil-soluble liquid can be determined according to the requirements for the viscosity of the internal phase fluid.

[0025] In the above-mentioned method for constructing micro-spiral flow, when the external phase fluid is an aqueous glycerol solution, the concentration of the aqueous glycerol solution can be determined according to the viscosity requirements of the external phase fluid in actual application; when the external phase fluid is an oil phase solvent, an oil phase solvent with suitable viscosity can be selected according to the viscosity requirements of the external phase fluid in actual application; when the external phase fluid is prepared by dissolving an oil-soluble liquid in an oil phase solvent, the viscosity of the oil-soluble liquid and the oil phase solvent can be selected and the concentration of the oil-soluble liquid in the external phase fluid can be determined according to the viscosity requirements of the external phase fluid in actual application.

[0026] In the above-mentioned method for constructing micro-spiral flow, surfactants can be added when preparing the inner phase fluid and the outer phase fluid.

[0027] In step (2) of the above-mentioned method for constructing micro-spiral flow, it is preferable to control the flow velocity of the inner phase fluid to be 0.1~0.5 m / s and the flow velocity of the outer phase fluid to be 0.001~0.015 m / s.

[0028] In the above-mentioned technical solution for constructing micro-spiral flow, the inner diameter of the conical orifice of the injection tube of the first-stage microfluidic device should ensure that the internal phase fluid can flow through sufficiently. It should not be too small to prevent excessive resistance when the high-viscosity internal phase fluid flows through or to prevent accidental impurities from clogging the conical orifice, thereby reducing the robustness of the microfluidic device. Preferably, the inner diameter of the conical orifice of the injection tube of the first-stage microfluidic device is controlled to be 60~130 μm.

[0029] In the above-mentioned technical solution for constructing micro-spiral flow, the inner diameter of the receiving tube of the first-stage microfluidic device should ensure that the internal phase fluid has sufficient space to develop its flow pattern in the receiving tube. Preferably, the inner diameter of the receiving tube of the first-stage microfluidic device is controlled to be 700~1500 μm.

[0030] When the internal phase fluid used in the above-mentioned method for constructing microspiral flows contains water-soluble photopolymerizable polymer monomers and water-soluble photoinitiators, or contains oil-soluble photopolymerizable polymer monomers and oil-soluble photoinitiators, during the construction of the microspiral flow, continuous or intermittent illumination of a specific wavelength is applied to the portion of the receiving tube where a stable microspiral flow has already formed. By applying light through an ultraviolet point light source, the water-soluble or oil-soluble photopolymerizable polymer monomers in the microspiral flow can undergo a photopolymerization reaction, solidifying the microspiral flow and transforming it into a microspiral. Furthermore, by controlling the duration of the applied illumination, the length of the prepared microspiral can be controlled. For example, continuous illumination can produce fibrous microspirals, while intermittent illumination can produce granular microspirals.

[0031] The present invention also provides a precise control method for micro-spiral flow structure. The method uses the above method to construct micro-spiral flow. In the process of constructing micro-spiral flow, by adjusting one or more of the following factors: viscosity of inner phase fluid, viscosity of outer phase fluid, inner diameter of conical nozzle of injection tube, inner diameter of receiving tube, flow velocity of inner phase fluid and flow velocity of outer phase fluid, one or more of the pitch, diameter, amplitude and frequency of micro-spiral flow constructed in step (2) can be adjusted.

[0032] This invention, through experiments, reveals that when constructing a micro-spiral flow using the aforementioned method, the pitch of the micro-spiral flow is most sensitive to the velocity of the external phase fluid, the diameter of the micro-spiral flow is most sensitive to the inner diameter of the injection tube's conical opening, and the frequency of the micro-spiral flow is most sensitive to the velocity of the internal phase fluid. Furthermore, when the edge of the micro-spiral flow adheres to the inner wall of the receiving tube, the inner diameter of the receiving tube limits the amplitude of the micro-spiral flow, thus controlling its amplitude. Based on these principles, precise and efficient control of the micro-spiral flow structure can be achieved.

[0033] Furthermore, in the technical solution of the above-mentioned precise control method for the micro-spiral flow structure, during the construction of the micro-spiral flow, the pitch of the micro-spiral flow is most sensitive to the flow velocity of the external phase fluid, and the pitch of the micro-spiral flow has a positive linear relationship with the flow velocity of the external phase fluid. Based on this relationship, the pitch of the micro-spiral flow can be controllably adjusted. The diameter of the micro-spiral flow is most sensitive to the inner diameter of the conical opening of the injection tube, and the diameter of the micro-spiral flow has a positive linear relationship with the inner diameter of the conical opening of the injection tube. Based on this relationship, the diameter of the micro-spiral flow can be controllably adjusted. When the edge of the micro-spiral flow is attached to the inner wall of the receiving tube, the amplitude of the micro-spiral flow is controlled by the inner diameter of the receiving tube. By increasing the inner diameter of the receiving tube, the amplitude of the micro-spiral flow can be increased. The frequency of the micro-spiral flow is most sensitive to the flow velocity of the internal phase fluid, and the frequency of the micro-spiral flow has a positive linear relationship with the flow velocity of the internal phase fluid. Based on this relationship, the frequency of the micro-spiral flow can be controllably adjusted.

[0034] This invention also provides a method for predicting the structural characteristics of micro-helical flows. Based on the relationships shown in equations (I) to (IV), the pitch, diameter, amplitude, and frequency of the micro-helical flow constructed using the above method can be predicted.

[0035] Formula (I)

[0036] Equation (II)

[0037] Equation (III)

[0038] Formula (IV)

[0039] In equations (I) to (IV), P , D , A , Ω These represent the pitch, diameter, amplitude, and frequency of the micro-spiral flow, respectively. D i , D o These are the inner diameters of the conical tip of the injection tube and the inner diameter of the receiving tube of the primary microfluidic device, respectively. u i , u o The flow velocities of the internal and external phase fluids are separated. μ i , μ o The viscosity of the internal phase fluid and the external phase fluid, respectively.

[0040] The above-mentioned method for predicting micro-spiral flow structures is based on the sodium alginate-water system. Therefore, this prediction method is particularly applicable to the sodium alginate-water system. The sodium alginate-water system refers to a system in which the inner phase fluid is prepared with sodium alginate and water, or the inner phase fluid is prepared with sodium alginate, water-soluble photopolymerizable polymer monomers, water-soluble photoinitiators and water, and water is used as the outer phase fluid.

[0041] The technical solution of the above-mentioned method for predicting the structural characteristics of micro-spiral flows can predict the pitch, diameter, amplitude, and frequency of micro-spiral flows constructed using the method described in this invention. In practical applications, based on the pitch, diameter, amplitude, and frequency of the micro-spiral flow to be prepared and some basic micro-spiral flow design conditions, the preparation conditions of the micro-spiral flow can be reverse-engineered and optimized according to equations (I) to (IV), thereby constructing a micro-spiral flow with structural characteristics that meet the expectations.

[0042] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0043] 1. This invention provides a method for constructing micro-spiral flows. This method achieves simple and controllable construction of micro-spiral flows based on velocity and viscosity differences. Specifically, it employs a high-viscosity inner-phase fluid and a low-viscosity outer-phase fluid. By controlling the viscosity ratio and flow rate ratio of the inner-phase fluid to the outer-phase fluid, a simple and controllable construction of micro-spiral flows is achieved based on the fluid rope-winding effect. Since the construction process does not involve cross-linking reactions and phase transitions, it can effectively solve the problems of microchannel blockage and poor micro-spiral flow morphology in traditional micro-spiral preparation methods, and can effectively improve the stability, continuity, and controllability of the micro-spiral flow forming process.

[0044] 2. The method for constructing microspiral flows described in this invention is applicable to a wide range of fluids, including not only non-Newtonian fluid systems but also Newtonian fluid systems (including all-aqueous and all-oil Newtonian systems). Microspirals can be prepared by applying light to the stable microspiral flow formed in the receiving tube to initiate a photocrosslinking reaction. Compared to traditional microspiral preparation methods, the method described in this invention can effectively broaden the selectivity and safety of solution systems, thereby better meeting the requirements of different application scenarios for microspirals and preparing microspirals with diverse functions.

[0045] 3. Based on the microspiral flow construction method described in this invention, this invention also provides a method for precise control of the microspiral flow structural characteristics. During the construction of the microspiral flow using the method described in this invention, the pitch, diameter, and frequency of the microspiral flow are most sensitive to the flow velocity of the external phase fluid, the inner diameter of the conical opening of the injection tube, and the flow velocity of the internal phase fluid, respectively. Furthermore, the pitch of the microspiral flow has a positive linear relationship with the flow velocity of the external phase fluid, the diameter of the microspiral flow has a positive linear relationship with the inner diameter of the conical opening of the injection tube, and the frequency of the microspiral flow has a positive linear relationship with the flow velocity of the internal phase fluid. Based on these relationships, the pitch, diameter, and frequency of the microspiral flow can be controllably adjusted. Simultaneously, when the edge of the microspiral flow adheres to the inner wall of the receiving tube, the amplitude of the microspiral flow is controlled by the inner diameter of the receiving tube. By increasing the inner diameter of the receiving tube, the amplitude of the microspiral flow can be increased. The method described in this invention solves the problem of difficulty in adjusting the diameter and amplitude when preparing microspirals using traditional crosslinking strategies, effectively solving the problem of coordinated control of multiple preparation parameters, and enabling precise control of the microspiral flow structural characteristics.

[0046] 4. This invention also provides a method for predicting the structural characteristics of micro-spiral flows. Based on the dimensionless relationship between the structural characteristics of the micro-spiral flow and the operating conditions obtained according to this invention, the pitch, diameter, amplitude, and frequency of the micro-spiral flow constructed using the method described in this invention can be predicted. This method has a good error range, and the effectiveness and accuracy of this method have been experimentally verified. In practical applications, based on the pitch, diameter, amplitude, and frequency of the micro-spiral flow to be prepared and some basic micro-spiral flow design conditions, the preparation conditions of the micro-spiral flow can be reverse-engineered and optimized according to the dimensionless relationship, thereby constructing a micro-spiral flow with structural characteristics that meet expectations. This provides an important means for the intelligent development and automatic design of micro-spirals. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of constructing a microhelical flow in a primary microfluidic device. In the diagram, 1 is the injection tube, 2 is the connecting tube, and 3 is the receiving tube. D i For the inner diameter of the cone opening, D o The inner diameter of the receiving tube. μ i For the viscosity of the internal phase fluid, μ o For the viscosity of the external phase fluid, u i For the flow rate of the internal phase fluid, u o The velocity of the external phase fluid; P For the pitch of micro-helical flow, D The diameter of the micro-spiral flow, A For the amplitude of the micro-helical flow, Ω denoted as the frequency of the micro-spiral flow.

[0048] Figure 2 Figure a shows the viscosity ratios of the internal and external phase fluids at different ratios. μ i / μ o ) and different internal phase fluid to external phase fluid velocity ratios ( u i / u o ) The flow pattern distribution of internal phase fluid under conditions, Figure 2 Figure b is the flow pattern spectrum of the microspiral flow obtained by regulation in a typical 2% NaAlg-H2O system.

[0049] Figure 3These are viscosity characteristic graphs for different solutions. Graph a shows the effect of NaAlg mass concentration on solution viscosity (non-Newtonian system) (shear rate 300 Hz), graph b shows the effect of shear rate on the apparent viscosity of NaAlg solution, graph c shows the effect of glycerol mass concentration on solution viscosity (Newtonian system), and graph d shows the effect of shear rate on the apparent viscosity of glycerol solution.

[0050] Figure 4 These are the three flow states exhibited by the internal phase fluid in the receiving tube under different operating conditions.

[0051] Figure 5 This is a diagram illustrating the control principles of the micro-spiral flow pattern spectrum. Figure a shows the patterns plotted under different internal phase fluid viscosities. u i - u o The flow pattern diagrams are shown in Figure b, which illustrates the effect of the internal phase fluid viscosity on the boundary line slope of the micro-helical flow pattern; and Figure c, which shows the flow pattern under different external phase fluid viscosities. u i - u o The flow pattern diagrams are shown in Figure d, which illustrates the effect of the external phase fluid viscosity on the boundary line slope of the micro-helical flow pattern, and Figure e, which is plotted under different injection tube conical inlet diameters. u i - u o The flow pattern spectrum, f-figure shows the effect of the inner diameter of the injection tube cone on the slope of the boundary line of the micro-spiral flow pattern spectrum.

[0052] Figure 6 The figures show the variation of the boundary intercept of the micro-spiral flow pattern spectrum. Figure a shows the effect of the viscosity of the inner phase fluid on the boundary intercept of the micro-spiral flow pattern spectrum, Figure b shows the effect of the viscosity of the outer phase fluid on the boundary intercept of the micro-spiral flow pattern spectrum, and Figure c shows the effect of the inner diameter of the injection tube cone on the boundary intercept of the micro-spiral flow pattern spectrum.

[0053] Figure 7 This data represents the construction and control of micro-helical flows within a Newtonian system. Figure a shows optical images of glycerol micro-helical flows constructed using a glycerol-water system at different external phase fluid velocities. Figure b shows the effect of external phase fluid velocity on the pitch of the glycerol micro-helical flow. Figure c shows optical images of PDMS micro-helical flows constructed using a PDMS-silicone oil system at different external phase fluid velocities. Figure d shows the effect of external phase fluid velocity on the pitch of the PDMS micro-helical flow.

[0054] Figure 8This diagram illustrates the effect of the flow velocities of the internal and external phase fluids on the pitch of the micro-spiral flow. Figure a shows optical images of the micro-spiral flow morphology constructed under different internal phase fluid flow velocities; Figure b shows the effect of the internal phase fluid flow velocity on the pitch; Figure c shows optical images of the micro-spiral flow morphology constructed under different external phase fluid flow velocities; and Figure d shows the effect of the external phase fluid flow velocity on the pitch. The units in Figures a and c are m / s.

[0055] Figure 9 The figures show the effects of other operating conditions on the pitch of the micro-spiral flow. Figure a shows optical images of the micro-spiral flow morphology constructed under different internal phase fluid viscosities; Figure b shows the pitch control effect of internal phase fluid viscosity; Figure c shows the micro-spiral flow morphology constructed under different external phase fluid viscosities; Figure d shows the pitch control effect of external phase fluid viscosity; Figure e shows the micro-spiral flow morphology constructed under different cone inner diameters; and Figure f shows the pitch control effect of cone inner diameter. The units in figures a, c, and e are m / s.

[0056] Figure 10 The figure shows the combined effect of operating conditions on the pitch of the micro-spiral flow. Figure a is a thermodynamic cloud diagram showing the effect of the two-phase fluid velocity on the pitch, and Figure b is the established prediction formula for the pitch of the micro-spiral flow.

[0057] Figure 11 These are the research results on the control of the diameter of micro-spiral flow. Figure a shows the effect of the internal phase fluid velocity on the diameter, Figure b shows the effect of the external phase fluid velocity on the diameter, Figure c shows the effect of the internal phase fluid viscosity on the diameter, Figure d shows the effect of the external phase fluid viscosity on the diameter, Figure e shows the effect of the cone inner diameter on the diameter, and Figure f shows the prediction formula for the diameter of micro-spiral flow.

[0058] Figure 12 These are the research results on the regulation of micro-spiral flow amplitude. Figure a shows the effect of the internal phase fluid velocity on the amplitude, Figure b shows the effect of the external phase fluid velocity on the amplitude, Figure c shows the effect of the internal phase fluid viscosity on the amplitude, Figure d shows the effect of the external phase fluid viscosity on the amplitude, Figure e shows the effect of the cone diameter on the amplitude, and Figure f shows the established prediction formula for micro-spiral flow amplitude.

[0059] Figure 13 These are the research results on the regulation of the frequency of micro-spiral flow. Figure a shows the effect of the internal phase fluid velocity on the frequency, Figure b shows the regulation of the frequency by the external phase fluid velocity, Figure c shows the effect of the internal phase fluid viscosity on the frequency, Figure d shows the effect of the external phase fluid viscosity on the frequency, Figure e shows the effect of the cone diameter on the frequency, and Figure f shows the prediction formula for the frequency of micro-spiral flow.

[0060] Figure 14 Figures a-b show the design flowchart of the micro-helical flow structure features, and optical images of the initial construction and iterative control of the micro-helical flow, respectively.

[0061] Figure 15 Images a through c are optical images of PEGDA@NaAlg microhelices prepared under different operating conditions. The pitch, diameter, and amplitude were adjusted in images a through c, respectively. Figure 15 The d~g diagram shows the difference between the structural features of the prepared microspiral and the predicted structural features of the microspiral flow. The d~g diagrams respectively show the differences between the pitch, diameter, amplitude and frequency of the experimentally prepared microspiral and the corresponding structural features of the predicted microspiral flow. Detailed Implementation

[0062] The following examples further illustrate the method for constructing micro-spiral flows and the method for precise control and prediction of their structural characteristics provided by this invention. It should be noted that the following examples are only for further illustration of this invention and should not be construed as limiting the scope of protection of this invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention will still fall within the scope of protection of this invention.

[0063] In the following embodiments, the primary microfluidic device used is a capillary coaxial device, the structural schematic of which is shown in the figure. Figure 1 As shown, the device includes an injection tube 1, a connecting tube 2, and a receiving tube 3, used in conjunction with an injection pump and a UV point light source. The injection tube 1 is made of a cylindrical glass capillary tube. One end of the cylindrical glass capillary tube is drawn into a tapered shape using a needle puller, and then sanded on sandpaper until the inner diameter of the tapered end is approximately 60-130 μm. The outer diameter of its cylindrical section is 960 μm, and the inner diameter is 700 μm. The connecting tube 2 is a square glass tube. After the square glass tube is cut to the required length using a glass cutter, both ends are sanded smooth. A square through-hole is provided in its center, with a cross-sectional dimension of 1×1 mm. The outer cross-sectional dimension of the square fiberglass tube is 1.2×1.2 mm. The receiving tube 3 is also made of a cylindrical glass capillary tube. After the cylindrical glass capillary tube is cut to the required length using a glass cutter, both ends are sanded smooth. After the injection tube 1, connecting tube 2 and receiving tube 3 are prepared, they are placed in anhydrous ethanol and deionized water respectively and ultrasonically vibrated for 60 seconds to clean impurities. Then they are dried with nitrogen and ready for use.

[0064] The construction process of the primary microfluidic device is as follows: Insert the outlet of injection tube 1 into the inlet of receiving tube 3; connect injection tube 1 and receiving tube 3 with connecting tube 2, ensuring that injection tube 1, connecting tube 2, and receiving tube 3 are coaxially arranged; fix a flat-tipped needle at the inlet end of injection tube 1 with AB glue, fix a flat-tipped needle at the inlet end of receiving tube 3 with AB glue, and connect the flat-tipped needle to a constant flow injection pump through a PE tube; seal the gap between the end area of ​​connecting tube 2 and injection tube 1 with AB glue. If it is necessary to solidify the constructed microspiral flow, the primary microfluidic device can be used in conjunction with an ultraviolet point light source. Place the ultraviolet point light source in the middle of the receiving tube (downstream of the location where a stable microspiral flow is formed) to apply ultraviolet light to irradiate the receiving tube to initiate the photopolymerization reaction of the photopolymerizable polymer monomers in the microspiral flow.

[0065] In the following embodiments, during the construction of microspiral flow using a primary microfluidic device, the high viscosity of the inner phase fluid leads to significant pressure loss along the injection process. Therefore, an appropriate inner phase fluid flow rate should be set to avoid excessive flow resistance that could result in inaccurate actual flow rate or damage to the primary microfluidic device.

[0066] Example 1

[0067] In this embodiment, a method for constructing micro-spiral flows based on viscosity and velocity differences is provided, and the steps are as follows:

[0068] (1) Prepare internal phase fluid and external phase fluid

[0069] Sodium alginate (NaAlg) and the red dye Rhodamine B were dissolved in deionized water to obtain an internal phase fluid. The mass fraction of NaAlg in the internal phase fluid ranged from 0.1% to 2.5%, and the mass fraction of Rhodamine B was 0.1%. To investigate the effect of the viscosity of the internal phase fluid on the construction of the micro-helical flow, internal phase fluids with viscosities of 10, 20, 30, 40, 50, 80, 100, 200, 300, 400, 700, and 800 mPa·s, as well as an internal phase fluid with a viscosity of 597 mPa·s, were prepared by adjusting the mass fraction of NaAlg in the internal phase fluid.

[0070] Deionized water (viscosity 1 mPa·s) was used as the external phase fluid.

[0071] (2) Constructing micro-spiral flow

[0072] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i =80μm, inner diameter of the receiving tube D o=1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0073] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0074] In this step, micro-spiral flows are constructed using internal phase fluids of different viscosities prepared in step (1), and the flow rate of the internal phase fluids is controlled. u i The control range is 0.033~0.332 m / s, which is the flow velocity of the external phase fluid. u o Multiple experiments were conducted within a control range of 0.001~0.013 m / s to investigate the effects of different viscosity ratios between the internal and external phase fluids. μ i / μ o ) and different internal phase fluid to external phase fluid velocity ratios ( u i / u o Can micro-helical flow be constructed under these conditions? The results are as follows: Figure 2 As shown in Figure a, "Straight" indicates that the internal fluid in the receiving tube behaves as a jet, "Blocked" indicates that the internal fluid in the receiving tube behaves as a blockage, and "Helical" indicates that the internal fluid in the receiving tube forms a micro-spiral flow. L 1 and L 2. The region between the two boundary lines is the region where micro-helical flow can be constructed (i.e., the helical region). u i / u o As the x-axis (denoted as) x ),by u i / u o The vertical axis (denoted as ) y ), L 1 and L The equations of the two boundary lines are as follows:

[0075] L 1:y = -0.0005 x 2 + 0.35 x +64, x = 50~1000

[0076] L 2: y = 10

[0077] In a typical experiment (2% NaAlg-H2O system), using an internal phase fluid with a NaAlg mass fraction of 2% (viscosity 597 mPa·s), the flow pattern spectrum of the micro-helical flow can be obtained by adjusting the flow rates of the two-phase fluids, such as... Figure 2 As shown in Figure b, "Straight" indicates that the internal fluid in the receiving tube behaves as a jet, "Blocked" indicates that the internal fluid in the receiving tube behaves as a blockage, and "Helical" indicates that the internal fluid in the receiving tube forms a micro-spiral flow. L u and L l The region between the two boundary lines is the area where micro-spiral flows can be constructed. Figure 4 The images show the flow patterns of the internal phase fluid in the receiving tube when the internal phase fluid velocity is different. When the internal phase fluid velocity is low, the internal phase fluid in the receiving tube exhibits a straight jet. When the internal phase fluid velocity is high, the internal phase fluid in the receiving tube exhibits a blocked flow. When the internal phase fluid velocity is appropriate, a micro-helical flow can be formed in the receiving tube.

[0078] Using deionized water as solvent, NaAlg solutions with concentrations ranging from 0 to 2.5 wt% and glycerol solutions with concentrations ranging from 0 to 70 wt% were prepared. Viscosities of the NaAlg and glycerol solutions at different concentrations were tested, and the results are as follows: Figure 3 As shown, the NaAlg solution exhibits high viscosity and significant shear-thinning properties, while the glycerol solution exhibits Newtonian fluid characteristics. With increasing internal phase fluid velocity, the flow regime of the NaAlg solution in the receiving tube sequentially changes from jet to spiral to blockage; conversely, with increasing external phase fluid velocity, the flow regime of the NaAlg solution in the receiving tube sequentially changes from blockage to spiral to jet.

[0079] Example 2

[0080] In this embodiment, the flow pattern spectrum of the micro-helical flow is controlled by adjusting the preparation conditions. The steps are as follows:

[0081] (1) Prepare internal phase fluid and external phase fluid

[0082] NaAlg and the red dye Rhodamine B were dissolved in deionized water to obtain an internal phase fluid; the mass fraction of NaAlg in the internal phase fluid was 1%–2.5%, and the mass fraction of Rhodamine B was 0.1%. To investigate the effect of the viscosity of the internal phase fluid on the construction of the micro-helical flow, internal phase fluids with viscosities of 186, 294, 431, and 597 mPa·s were prepared by adjusting the mass fraction of NaAlg in the internal phase fluid.

[0083] Glycerol was dissolved in deionized water to obtain an external phase fluid; the mass fraction of glycerol in the external phase fluid ranged from 0% to 70%. To investigate the effect of the viscosity of the external phase fluid on the construction of the micro-spiral flow, external phase fluids with viscosities of 1.0, 1.3, 1.8, and 2.5 mPa·s were prepared by adjusting the mass fraction of glycerol in the external phase fluid.

[0084] (2) Micro-spiral flow was constructed using internal phase fluids of different viscosities.

[0085] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i = 80μm, inner diameter of the receiving tube D o = 1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0086] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0087] In this step, deionized water is used as the external phase fluid, and the following methods are employed: μ i Micro-spiral flows were constructed using internal phase fluids with values ​​of 186, 294, 431, and 597 mPa·s, and the flow was controlled. u i The control range is 0.033~0.400 m / s. u o Multiple experiments were conducted with the control range being 0.001~0.020 m / s.

[0088] The flow velocity regulation of the two-phase fluid was studied under the viscosity conditions of each internal phase fluid, and the corresponding flow regimes were recorded and plotted. u i - u o Flow pattern spectrum (see Figure 5 (Figure a); the feasible operating conditions of the micro-helical flow are determined by... L u and L l Two boundary lines were used for control, and the slope of the upper boundary line showed a significant change (see...). Figure 5 Figure b shows that it has a significant regulatory effect on the micro-spiral flow, while the slope of the lower boundary line changes only slightly, indicating that the volume confinement of the micro-spiral flow is the main cause of the blockage flow, and does not change significantly with the viscosity of the internal phase fluid. L u and L l The slope of the two boundary lines k The control relationship is as follows:

[0089] k - L u : y = 0.0001 x + 0.0129

[0090] k - L l : y = 0.00002 x + 0.0048

[0091] The intercepts of the upper and lower boundary lines show positive and negative correlation trends, respectively, with relatively small changes (see...). Figure 6 Figure a) shows a favorable effect on feasible operating conditions; L u and L l Intercepts of the two boundary lines b The control relationship is as follows:

[0092] b - L u : y = 0.000004 x + 0.0017

[0093] b - L l : y = -0.000002 x + 0.0015

[0094] (3) Constructing micro-spiral flow using external phase fluids of different viscosities

[0095] The micro-spiral flow is constructed using the apparatus described in step (2) following the operation of step (2). In this step, the apparatus used... μ o Micro-spiral flows were constructed using external phase fluids with concentrations of 1.0, 1.3, 1.8, and 2.5 mPa·s, and the flow was controlled. μ i = 431 mPa·s, control u i The control range is 0.033~0.400 m / s. u o Multiple experiments were conducted with the control range being 0.001~0.020 m / s.

[0096] The flow velocity regulation of the two-phase fluid was studied under each external phase fluid viscosity condition, and the corresponding flow regimes were recorded and plotted. u i - u o Flow pattern spectrum (see Figure 5 (See diagram c); in particular, the slopes of the upper and lower boundary lines (see diagram c). Figure 5 (d-plot) and intercept (see d-plot) Figure 6 The changes in Figure b) are not significant, indicating that the viscosity of the external phase fluid has little effect on the feasible range of the helical flow, but only affects the structural parameters of the micro-helical flow (the pitch, diameter, amplitude, and frequency of the micro-helical flow).

[0097] (4) Micro-spiral flow was constructed using injection tubes with different conical inner diameters.

[0098] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i =60, 80, 100, 120 μm, inner diameter of the receiving tube D o =1000 μm. Construct the microhelical flow according to step (2). In this step, control μ i = 294 mPa·s μ o = 1 mPa·s, control u i The control range is 0.033~0.400 m / s. u o The control range is 0.001~0.020 m / s, and multiple sets of experiments were conducted using injection tubes with different conical inner diameters.

[0099] The flow velocity regulation of the two-phase fluid was studied under each conical inlet diameter condition, and the corresponding flow regime was recorded and plotted. u i - u o Flow pattern spectrum (see Figure 5 (See Figure e); where the slopes of the upper and lower boundary lines show significant changes (see Figure e). Figure 5 Figure f shows that the inner diameter of the conical nozzle of the injection tube has a significant regulatory effect on the micro-helical flow pattern, and increasing the inner diameter of the conical nozzle is beneficial to increasing the feasible range of the micro-helical flow pattern. In addition, the intercepts of the upper and lower boundary lines show positive and negative correlation trends, respectively, with relatively large variations (see Figure f). Figure 6 (Figure c). L u and L l The slope of the two boundary lines k and intercept b The control relationship is as follows:

[0100] k - L u : y = 0.0006 x - 0.014

[0101] k - L l : y = 0.0002 x - 0.0095

[0102] b - L u : y = 0.00003 x + 0.0005

[0103] b - L l : y = -0.00002 x + 0.0027

[0104] Example 3

[0105] In this embodiment, a method for constructing micro-helical flows based on viscosity and velocity differences is provided. Specifically, a Newtonian fluid is used to construct the micro-helical flow, and the steps are as follows:

[0106] (1) Prepare internal phase fluid and external phase fluid

[0107] Aqueous phase system (Glycerol-H2O): The red dye Rhodamine B was dissolved in glycerol to obtain the inner phase fluid; the mass fraction of Rhodamine B in this inner phase fluid was 0.1%, and the viscosity of the inner phase fluid was 887 mPa·s. Deionized water was used as the outer phase fluid.

[0108] Oil phase system (PDMS-Silicone oil): Lumogen Red 300 was dissolved in polydimethylsiloxane (PDMS) to obtain the inner phase fluid; the mass fraction of Lumogen Red 300 in this inner phase fluid was 3%, and the viscosity of the inner phase fluid was 4000 mPa·s. Silicone oil (viscosity 1 mPa·s) was used as the outer phase fluid.

[0109] (2) Constructing micro-spiral flow

[0110] A microhelical flow is constructed using a single-stage microfluidic device. In an aqueous system, the inner diameter of the conical orifice of the injection tube of the single-stage microfluidic device is... D i = 80 μm, inner diameter of the receiving tube D o = 500 μm. In the oil phase system, the inner diameter of the tapered inlet of the injection tube of the primary microfluidic device... D i = 80 μm, inner diameter of the receiving tube D o = 700 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0111] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0112] For aqueous systems: control u i = 0.166 m / s, control u o The flow rate was controlled within the range of 0.015~0.036 m / s to construct a micro-spiral flow. The inner phase fluid formed a well-defined micro-spiral structure in the receiving tube. By adjusting the outer phase fluid velocity, the morphology of the micro-spiral flow exhibited a regular changing trend, such as... Figure 7 As shown in Figure a, the horizontal axis of this figure represents the external phase fluid velocity (…). u o , m / s); set parallel groups of internal phase fluid velocities respectively ( u i = 0.133, 0.166, 0.199 m / s), micro-helical flows were constructed under different external phase fluid velocities. In each parallel group, the pitch of the constructed micro-helical flows exhibited a good linear control relationship with the external phase fluid velocity, such as... Figure 7 As shown in Figure b.

[0113] For oil phase systems: control u i = 0.133 m / s, respectively controlled u o The micro-spiral flow was constructed within a control range of 0.006~0.013 m / s. The inner phase fluid formed a well-defined micro-spiral structure in the receiving tube. By adjusting the outer phase fluid velocity, the morphology of the micro-spiral flow exhibited a regular changing trend, such as... Figure 7 As shown in Figure c, the horizontal axis of this figure represents the external phase fluid velocity ( u o , m / s); set parallel groups of internal phase fluid velocities respectively ( u i = 0.099, 0.133, 0.166 m / s), micro-helical flows were constructed under different external phase fluid velocities. In each parallel group, the pitch of the constructed micro-helical flows exhibited a good linear control relationship with the external phase fluid velocity, such as... Figure 7 As shown in Figure d.

[0114] As can be seen from this embodiment and Embodiment 1, the method for constructing micro-spiral flow according to the present invention has good scalability for applicable fluid systems. In addition to being applicable to non-Newtonian fluid systems, it is also applicable to Newtonian fluid systems.

[0115] Example 4

[0116] In this embodiment, the pitch control mechanism in the micro-helical flow structure is examined, and the steps are as follows:

[0117] (1) Prepare internal phase fluid and external phase fluid

[0118] NaAlg and the red dye Rhodamine B were dissolved in deionized water to obtain the inner phase fluid; the mass fraction of Rhodamine B was 0.1%; the viscosity of the inner phase fluid was adjusted to 95~419 mPa·s by adjusting the mass fraction of NaAlg in the inner phase fluid, and deionized water was used as the outer phase fluid.

[0119] Glycerol was dissolved in deionized water to obtain the external phase fluid. The viscosity of the external phase fluid was adjusted to 1.0~22.5 mPa·s by adjusting the mass fraction of glycerol in the external phase fluid. At this time, a NaAlg solution with a viscosity of 306 mPa·s was used as the internal phase fluid.

[0120] (2) Constructing micro-spiral flow

[0121] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i =60~130 μm, inner diameter of the receiving tube D o =1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0122] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0123] First, this step is done in D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u o Under the condition that the control range is 0.0050~0.0075 m / s, control u i The control range is 0.066~0.249 m / s to construct a micro-helical flow, and then... D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u i Under the condition that the control range is 0.166~0.298m / s, control u o The control range is 0.0031~0.0100 m / s to construct micro-spiral flow.

[0124] Pitch has a significant impact on the performance of micro-helical flows and is the most important control characteristic. In pitch adjustment, the flow velocities of the two phases have opposite effects on the morphology of the micro-helical flow. With the increase of the inner phase fluid velocity... u i With the increase of [unclear], the micro-spiral flow always exhibits a good spiral morphology (see [unclear]). Figure 8 (See Figure a), and the pitch shows a significant decreasing trend, exhibiting a negative power-law relationship (see Figure a). Figure 8 (See graph b, the relationship is as follows). Specifically, the coefficients and exponents respectively increase with... u i The axial compressive stress increases and decreases with the increase of the outer phase fluid. From the perspective of energy conversion, the elastic potential energy accumulated in the inner phase fluid increases, and this energy cannot be dissipated through the shearing action of the outer phase fluid. Therefore, the packing density of the inner phase fluid increases within a limited space, which manifests as a decrease in pitch. u i The increase in the value of the internal phase fluid makes it more prone to instability and significantly accelerates the occurrence of spiral curling.

[0125] P ( u i ): y = 124.83 x -0.627 , R 2 = 0.99 ( u o = 0.005 m / s)

[0126] Similarly, with the external phase fluid velocity u o With the increase of [unclear], the micro-spiral flow also exhibits an ideal morphology (see [unclear]). Figure 8 (See Figure c), and the pitch shows a linear increasing trend (see Figure c). Figure 8 The relationship is shown in the d-plot below. Specifically, the slope increases with... u o The pitch decreases with increasing external shear, but remains within a constant range (30-50). When the external shear force increases, the internal fluid exhibits delayed instability; when the tensile force increases, the internal fluid exhibits a larger pitch. The results show that precise pitch control can be achieved through a wider flow window. Furthermore, compared to the control strategies of traditional crosslinking methods, the method described in this invention demonstrates excellent control relationships and extremely high controllability.

[0127] P ( u o ): y = 65232 x + 43, R2 = 0.99 ( u i = 0.166 m / s)

[0128] Secondly, this step is in D i = 80 μm u i = 0.166 m / s μ o = 1 mPa·s, u o Under the condition that the control range is 0.0031~0.0044 m / s, control μ i The control range is 95~359 mPa·s to construct micro-helical flow, and then... D i = 80 μm u i = 0.166 m / s u i = 306 mPa·s, u o Under the condition that the control range is 0.0050~0.0063 m / s, control μ o The control range is 1.0~22.5 mPa·s to construct micro-spiral flow.

[0129] As the viscosity of the internal phase fluid increases, the morphology of the micro-spiral flow gradually improves (see...). Figure 9 (See Figure a), while the pitch remains constant at around 300 μm (see Figure a). Figure 9 (See Figure b). When the viscosity of the inner phase fluid exceeds the critical viscosity at the stable phase interface, the inner phase fluid can form a stable helical structure and enhance its buckling ability, thereby obtaining a superior morphology and greater helicity. As the viscosity of the outer phase fluid increases, the micro-helical flow also exhibits a distinct helical morphology (see Figure b). Figure 9 (See Figure c), and the pitch shows a slight decreasing trend, exhibiting a negative power-law relationship (see Figure c). Figure 9 The relationship is shown in the d-plot below. As the viscosity of the outer phase fluid increases, the coefficients and exponents increase and decrease, respectively. When the shearing effect of the outer phase fluid intensifies, the axial compressive stress of the inner phase fluid decreases. Unexpectedly, the micro-spiral flow did not exhibit the expected pitching elongation, but instead showed bilateral contraction towards the central axis.

[0130] P ( μ o ): y = 371.84 x -0.06 ,R 2 = 0.98 ( u o = 0.0056 m / s)

[0131] Third, this step is in μ i = 217 mPa·s μ o = 1 mPa·s u i = 0.199 m / s, u o Under the condition that the control range is 0.0038~0.0063 m / s, control D i The control range is 60~130 μm to construct micro-spiral flow.

[0132] As the inner diameter of the conical opening increases, the pitch of the micro-spiral flow increases logarithmically (see...). Figure 9 The e~f graph shows the relationship as follows. As the inner diameter of the conical opening increases, the coefficient and exponent increase and decrease, respectively. Especially... D i Within the range of 60~100 μm, the micro-spiral flow does not contact the inner wall of the receiving tube, exhibiting an optimal spiral morphology. According to Euler's buckling theory, increasing the inner diameter of the cone significantly increases the diameter of the inner phase fluid, resulting in a constrained outlet space. During buckling, the moment of inertia of the cross section increases, thus exhibiting an increased rolling amplitude and increased pitching under constant velocity conditions.

[0133] P ( D i ): y = 380.28ln( x )-1308.7, R 2 = 0.99 ( u o = 0.0050 m / s)

[0134] The pitch has a crucial impact on the performance of microhelices. A thermodynamic contour plot of the effect of the flow velocity of the two-phase fluid on the pitch was plotted using experimental data from Examples 4 and 5. Figure 10 As shown in Figure a ( μ i = 217 mPa·s, μ o = 1 mPa·s, D i =80 μm, D o= 1000 μm), by adjusting the flow rates of the inner and outer phase fluids, the pitch of the micro-spiral flow can be easily and efficiently controlled, and it exhibits a good distribution law. Therefore, the thermodynamic cloud map of the effect of the flow rates of the two phase fluids on the pitch can be used to further guide the design of operating conditions.

[0135] Meanwhile, dimensionless quantities of velocity, viscosity, and size were established using Backingham's theorem, and a micro-spiral flow pitch prediction formula with an error range of ±15% was fitted (see...). Figure 10 The relationship is shown in Figure b, as illustrated in Equation (I). The results indicate that the pitch of the micro-spiral flow is mainly determined by the velocity ratio between the inner and outer phase fluids. u i / u o ), and the ratio of the inner diameter of the conical tip of the injection tube to the inner diameter of the receiving tube ( D i / D o ) control, among which the negative exponential effect of the flow rate ratio (-0.73) is particularly significant, while the viscosity ratio ( μ i / μ o The impact of ) is relatively weak.

[0136] Formula (I)

[0137] Example 5

[0138] In this embodiment, the diameter regulation law in the micro-spiral flow structure is examined, and the steps are as follows:

[0139] (1) Prepare internal phase fluid and external phase fluid

[0140] Same as step (1) in Example 4.

[0141] (2) Constructing micro-spiral flow

[0142] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i = 60~130 μm, inner diameter of the receiving tube D o = 1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0143] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0144] First, this step is done in D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u o Under the condition that the control range is 0.0038~0.0063 m / s, control u i The control range is 0.030~0.350 m / s to construct a micro-helical flow, and then... D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u i Under the condition that the control range is 0.099~0.232 m / s, control u o The control range is 0.002~0.012 m / s to construct micro-spiral flow.

[0145] Secondly, this step is first in D i = 80 μm μ o = 1 mPa·s u i = 0.166 m / s, u o Under the condition that the control range is 0.0038~0.0063 m / s, control μ i The control range is 95~419 mPa·s to construct micro-helical flow, and then... D i = 80 μm μ i = 306 mPa·s u i = 0.265 m / s u oUnder the condition that the control range is 0.0050~0.0063 m / s, control μ o The control range is 1.0~22.5 mPa·s to construct micro-spiral flow.

[0146] Third, this step is in μ i = 217 mPa·s μ o = 1 mPa·s u i = 0.199 m / s, u o Under the condition that the control range is 0.0044~0.0056 m / s, control D i The control range is 60~130 μm to construct micro-spiral flow.

[0147] In diameter regulation, the diameter is positively correlated with the flow velocity of the two-phase fluid, exhibiting a power-law relationship and a linear relationship, respectively (see...). Figure 11 (See Figures a-b). Specifically, during axial development, the inner phase fluid is compressed and expanded at the conical opening due to the Barus effect, resulting in a sudden increase in diameter (80-130 μm). Furthermore, according to volume conservation, the flow velocity suddenly decreases, releasing elastic potential energy during spatial transformation. Subsequently, under the shearing action of the outer phase fluid, the diameter gradually increases, further releasing energy. At this point, the inner phase fluid cannot reach energy balance and cannot break through the phase interface, leading to buckling instability and continuous coiling in space to achieve maximum energy release. Finally, the inner phase fluid, under the synergistic effect of the outer phase fluid, generates a continuous spatial spiral structure. Increasing the flow velocity of the inner phase fluid, although increasing its volume, is limited by the non-Newtonian nature of the fluid, meaning its diameter can only increase slightly. The diameter exhibits a negative logarithmic and a positive power-law relationship with the viscosity of the two phases, respectively (see Figures a-b). Figure 11 (See figures c-d). As the viscosity of the inner phase fluid increases, its shear resistance increases, limiting volume expansion and thus reducing the diameter. Simultaneously, as the viscosity of the outer phase fluid increases, the micro-spiral flow tends to contract axially, resulting in a slight increase in diameter to maintain volume conservation. Furthermore, the diameter shows a linear positive correlation with the inner diameter of the cone (see Figure c-d). Figure 11 The relationship is shown in the e-graph (see below). The slope follows... D i The diameter increases with increasing diameter, while the intercept remains within a constant range (25~35). According to the Barus effect, narrowing of the inner diameter is the key factor limiting the development of the inner diameter of non-Newtonian fluids. Therefore, the larger the inner diameter of the cone, the larger the diameter of the micro-spiral flow. Generally, the diameter can eventually be increased to 2.5 times the inner diameter of the cone.

[0148] D ( D i ): y = 1.8727 x +32, R 2 = 0.98 ( u o = 0.0044 m / s)

[0149] Finally, the micro-spiral flow diameter prediction formula was fitted using dimensionless fitting (see...). Figure 11 The relationship is shown in the f-plot (as shown in Equation (II)), with an error limit of ±15%. Compared with existing crosslinking methods that can only construct diameters with the same inner diameter as the cone opening, the method described in this invention can significantly adjust the diameter of the micro-spiral flow within the range of 100~300 μm.

[0150] Equation (II)

[0151] Example 6

[0152] In this embodiment, the amplitude regulation law in the micro-helical flow structure is examined, and the steps are as follows:

[0153] (1) Prepare internal phase fluid and external phase fluid

[0154] Same as step (1) in Example 4.

[0155] (2) Constructing micro-spiral flow

[0156] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i = 60~130 μm, inner diameter of the receiving tube D o =1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0157] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0158] First, this step is done in D i= 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u o Under the condition that the control range is 0.0038~0.0063 m / s, control u i The control range is 0.050~0.350 m / s to construct a micro-helical flow, and then... D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u i Under the condition that the control range is 0.166~0.298 m / s, control u o The control range is 0.003~0.016 m / s to construct micro-spiral flow.

[0159] Secondly, this step is first in D i = 80 μm μ o = 1 mPa·s u i = 0.166 m / s, u o Under the condition that the control range is 0.0031~0.0044 m / s, control μ i The control range is 95~419 mPa·s to construct micro-helical flow, and then... D i = 80 μm μ i = 306 mPa·s u i = 0.265 m / s u o Under the condition that the control range is 0.0050~0.0063 m / s, control μ o The control range is 1.0~22.5 mPa·s to construct micro-spiral flow.

[0160] Third, this step is in μ i = 217 mPa·s μ o = 1 mPa·s ui = 0.199 m / s, u o Under the condition that the control range is 0.0038~0.0063 m / s, control D i The control range is 60~130 μm to construct micro-spiral flow.

[0161] In amplitude regulation, the amplitude is inversely proportional to the flow velocity of the two-phase fluid. Increasing the flow velocity of the inner phase fluid slightly increases the swirling amplitude of the micro-spiral flow releasing energy, and the amplitude increases logarithmically (see...). Figure 12 (See Figure a). Increased external phase fluid velocity enhances the effect of external phase shear on the micro-helical flow, until it is stretched to a two-dimensional oscillation or jet, thus exhibiting a linear decreasing trend in amplitude (see Figure a). Figure 12 (See Figure b). Similarly, the amplitude is inversely proportional to the viscosity of the two-phase fluid. Increasing the viscosity of the inner phase fluid enhances its shear resistance, allowing for a larger coil space, exhibiting a positive linear relationship (see Figure b). Figure 12 (See Figure c). Similar to how the moment of inertia of a microfluidic cross-section increases as the inner diameter gradually decreases, this adjustment enhances the microfluidic's coiling ability, thereby creating a larger amplitude (see Figure c). Figure 12 (See Figure c). The increase in external phase fluid viscosity is consistent with the previously analyzed contraction trend, exhibiting a negative logarithmic relationship in amplitude (see Figure c). Figure 12 (The d-graph). Especially when D i When the amplitude exceeds 100 μm, due to the limitation of the inner wall of the receiving tube, the maximum amplitude reaches 1000 μm (see...). Figure 12 (Figure e). The flow near the critical amplitude is defined as free flow and confined flow, respectively. In confined flow, the micro-helical flow is similar to the flow state of the cross-linking method, further deformed under the friction of the inner wall, which is not conducive to adjusting structural features. Meanwhile, in the fitted data ( Figure 12 A poor correlation was observed in the f1 region of the f-plot, indicating that the micro-spiral flow should be regulated under free-flow conditions when designing operating conditions. Therefore, by adjusting the inner diameter of the receiving tube, micro-spiral flows with a large amplitude range from micrometers to millimeters can be generated. Finally, the micro-spiral flow amplitude prediction formula was fitted using dimensionless fitting (see...). Figure 12 The relationship is shown in the f-plot (as shown in equation (III)), with an error limit of ±15%.

[0162] Equation (III)

[0163] Example 7

[0164] In this embodiment, the frequency modulation law in the micro-spiral flow structure characteristics is examined, and the steps are as follows:

[0165] (1) Prepare internal phase fluid and external phase fluid

[0166] Same as step (1) in Example 4.

[0167] (2) Constructing micro-spiral flow

[0168] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i = 60~130 μm, inner diameter of the receiving tube D o =1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0169] The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube through the PE tube using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid decelerates, and at the same time, it forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability. After the instability ends, a stable micro-spiral flow is formed in the middle of the receiving tube.

[0170] First, this step is done in D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u o Under the condition that the control range is 0.0038~0.0063 m / s, control u i The control range is 0.100~0.350 m / s to construct a micro-helical flow, and then... D i = 80 μm μ i = 217 mPa·s μ o = 1 mPa·s u i Under the condition that the control range is 0.166~0.298 m / s, control u o The control range is 0.004~0.008 m / s to construct micro-spiral flow.

[0171] Secondly, this step is first in D i= 80 μm μ o = 1 mPa·s u i = 0.166 m / s, u o Under the condition that the control range is 0.0031~0.0044 m / s, control μ i The control range is 95~419 mPa·s to construct micro-helical flow, and then... D i = 80 μm μ i = 306 mPa·s u i = 0.265 m / s u o Under the condition that the control range is 0.0050~0.0063 m / s, control μ o The control range is 1.0~22.5 mPa·s to construct micro-spiral flow.

[0172] Third, this step is in μ i = 217 mPa·s μ o = 1 mPa·s u i = 0.199 m / s, u o Under the condition that the control range is 0.0038~0.0063 m / s, control D i The control range is 60~130 μm to construct micro-spiral flow.

[0173] Regarding frequency (i.e., the number of pitches generated per unit time), the frequency is linearly and positively correlated with the flow velocity of the two-phase fluid (see...). Figure 13 (See Figures a-b). Based on the volume conservation of the inner phase fluid, the inner phase fluid velocity is the dominant factor in frequency regulation, while the outer phase fluid velocity has only a slight enhancing effect on the frequency. Time analysis shows that the micro-spiral flow exhibits good frequency stability during fabrication, thus ensuring the uniformity of structural characteristics. The frequency has an anti-linear relationship with the viscosity of the two-phase fluid (see Figures a-b). Figure 13 (See figures c-d). As the viscosity of the inner phase fluid increases, the turbulence amplitude of the inner phase fluid increases, leading to a decrease in frequency. Conversely, when the viscosity of the outer phase fluid increases, the micro-spiral flow undergoes significant contraction, exhibiting the opposite trend, resulting in an increase in frequency. Furthermore, the frequency exhibits a negative exponential relationship with the inner diameter of the cone (see Figure c-d). Figure 13(See diagram e), its regulating effect is similar to the increase in viscosity of the internal phase fluid. Finally, the frequency prediction formula for the micro-spiral flow is predicted using dimensionless fitting (see diagram e). Figure 13 The relationship is shown in the f-plot (IV), with an error limit of ±15%.

[0174] Formula (IV)

[0175] As can be seen from Examples 4-7, when constructing a micro-spiral flow using the method described in this invention, one or more of the following factors can be adjusted: the viscosity of the inner phase fluid, the viscosity of the outer phase fluid, the inner diameter of the conical opening of the injection tube, the inner diameter of the receiving tube, the flow rate of the inner phase fluid, and the flow rate of the outer phase fluid. This adjustment can control the pitch, diameter, amplitude, and frequency of the constructed micro-spiral flow.

[0176] Furthermore, during the construction of the micro-spiral flow, the pitch of the micro-spiral flow is most sensitive to the velocity of the external phase fluid, exhibiting a positive linear relationship. This relationship allows for controllable adjustment of the micro-spiral flow pitch. Similarly, the diameter of the micro-spiral flow is most sensitive to the inner diameter of the conical opening of the injection tube, also exhibiting a positive linear relationship. This relationship allows for controllable adjustment of the micro-spiral flow diameter. The frequency of the micro-spiral flow is most sensitive to the velocity of the internal phase fluid, exhibiting a positive linear relationship. This relationship allows for controllable adjustment of the micro-spiral flow frequency. When the edge of the micro-spiral flow adheres to the inner wall of the receiving tube, the amplitude of the micro-spiral flow is controlled by the inner diameter of the receiving tube. Increasing the inner diameter of the receiving tube increases the amplitude of the micro-spiral flow. Based on these principles, in practical applications, the pitch, diameter, amplitude, and frequency of the micro-spiral flow can be flexibly and controllably adjusted according to specific application requirements.

[0177] Example 8

[0178] The prediction formulas for the pitch, diameter, amplitude, and frequency of the micro-spiral flow established in Examples 4-7 are summarized below:

[0179] Formula (I)

[0180] Equation (II)

[0181] Equation (III)

[0182] Formula (IV)

[0183] In equations (I) to (IV), P , D , A , Ω These represent the pitch, diameter, amplitude, and frequency of the micro-spiral flow, respectively.D i , D o These are the inner diameters of the conical tip of the injection tube and the inner diameter of the receiving tube of the primary microfluidic device, respectively. u i , u o The flow velocities of the internal and external phase fluids are separated. μ i , μ o The viscosity of the internal phase fluid and the external phase fluid, respectively.

[0184] In the error verification of the prediction formulas shown in equations (I) to (IV), the data are all within ±15%, indicating a good error range. The established prediction formulas can be used to calculate and guide the construction and control of micro-spiral flows. Based on the relationships shown in equations (I) to (IV), the pitch, diameter, amplitude, and frequency of the micro-spiral flow constructed using the method described in this invention can be predicted. In practical applications, based on the pitch, diameter, amplitude, and frequency of the micro-spiral flow to be prepared and some basic design conditions, the preparation conditions of the micro-spiral flow can be reverse-engineered and optimized according to equations (I) to (IV), thereby constructing a micro-spiral flow with the expected structure. A specific example is given below.

[0185] The design follows the technical approach of "fluid system - microchannel size of microfluidic device - flow rate of two-phase fluid", such as... Figure 14 As shown in Figure a, the steps are as follows:

[0186] (1) Product design parameters of micro-spiral flow

[0187] The product design parameters for the proposed micro-spiral flow are determined based on actual application requirements, namely: pitch. P = 400 μm, diameter D = 200 μm, amplitude A = 900 μm microspiral flow.

[0188] (2) Preliminary selection of construction conditions

[0189] Based on practical application requirements, the fluid system selected was 1.5% NaAlg-H2O prepared at room temperature (20 ℃). Specifically, the inner phase fluid was a 1.5% NaAlg aqueous solution, and the outer phase fluid was deionized water. After determining the composition of the inner and outer phase fluids, the following can be determined: μ i = 294 mPa·s μ o = 1 mPa·s. Preset Di = 80 μm D o =1000 μm, preset u i = 0.199 m / s u o = 0.0050 m / s.

[0190] (3) Construct micro-spiral flow according to the initially selected construction conditions.

[0191] Following the conditions initially selected in step (2), and referring to the operation in step (2) of Example 4, a micro-spiral flow was constructed. An optical image of the constructed micro-spiral flow is shown below. Figure 14 As shown in Figure b1, its pitch, diameter, and amplitude were measured, and the results are as follows: P = 423 μm, diameter D = 172 μm, amplitude A = 812 μm.

[0192] (4) Optimize preparation conditions

[0193] The pitch of the micro-spiral flow constructed in step (3) is slightly larger than the design value, the diameter is slightly smaller than the design value, and the amplitude is significantly smaller than the design value. Adjustments are made according to the relationships shown in equations (I) to (IV). D i / D o , u i / u o and μ i / μ o The value of is used to reduce the pitch of the micro-spiral, increase its diameter, and increase its amplitude to get closer to the design value.

[0194] The final optimized construction conditions for the micro-spiral flow were determined as follows: a NaAlg aqueous solution with a NaAlg mass fraction of 1.6% was used as the inner phase fluid, and deionized water was used as the outer phase fluid. After determining the composition of the inner and outer phase fluids, the following conditions could be determined: μ i = 345 mPa·s μ o = 1 mPa·s. D i = 85 μm D o = 1000 μm, u i = 0.191 m / s u o= 0.0047 m / s.

[0195] (5) Construct micro-spiral flow according to the optimized construction conditions

[0196] Following the optimized conditions in step (4), and referring to step (2) of Example 5, a micro-spiral flow was constructed. An optical image of the constructed micro-spiral flow is shown below. Figure 14 As shown in Figure b2, its pitch, diameter, and amplitude were measured, and the results are as follows: P = 399 μm, diameter D = 195 μm, amplitude A = 915 μm, which is very close to the design value in step (1). This shows that the relationships shown in equations (I) to (IV) can be used to design and optimize the construction conditions of micro-spiral flow, so as to more conveniently and efficiently construct micro-spiral flow with a structure that meets the design goals.

[0197] Example 9

[0198] In this embodiment, the reliability and error rate of the previously established prediction formula for the micro-helical flow structure characteristics are examined in the fabrication of micro-helices. The steps are as follows:

[0199] (1) Prepare internal phase fluid and external phase fluid

[0200] Polyethylene glycol dimethacrylate (PEGDA) and 2-hydroxy-2-methyl-1-phenyl-1-propanone (HMPP) were added to deionized water and mixed thoroughly. Then, surfactant F127 was added, and the mixture was stirred thoroughly to emulsify. Next, NaAlg was added, and the mixture was stirred in a 40 °C water bath until completely dissolved, yielding the inner phase fluid. The concentrations of PEGDA, HMPP, F127, and NaAlg in the inner phase fluid were 15 wt%, 1.5 wt%, 1 wt%, and 1.75 wt%, respectively. The viscosity of the inner phase fluid was 628 mPa·s. Deionized water was used as the outer phase fluid.

[0201] (2) Constructing and solidifying micro-spiral flow to form micro-spirals

[0202] A microhelical flow is constructed using a single-stage microfluidic device. The inner diameter of the tapered inlet of the injection tube of the single-stage microfluidic device is... D i = 60~110 μm, inner diameter of the receiving tube D o =1000 μm. The first-stage microfluidic device is arranged vertically with the injection tube at the top and the receiving tube at the bottom. A receiving container containing receiving liquid (deionized water) is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container.

[0203] The inner and outer phase fluids were continuously injected into the injection tube and receiving tube respectively using a constant flow injection pump through a PE tube. The inner phase fluid jetted and expanded into the receiving tube from the tapered opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid slowed down, and it formed a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid became unstable and coiled due to buckling instability. After the instability ended, a stable micro-spiral flow was formed in the middle of the receiving tube. Ultraviolet light was applied to the middle and slightly downstream of the receiving tube using an ultraviolet point light source to induce a photopolymerization reaction of PEGDA in the micro-spiral flow, solidifying the micro-spiral flow to obtain PEGDA microspirals.

[0204] In this step, the flow rate of the inner phase fluid is controlled to be 0.100~0.350 m / s, and the flow rate of the outer phase fluid is controlled to be 0.004~0.008 m / s. A micro-spiral flow is constructed by adjusting the flow rates of the two phase fluids and the inner diameter of the conical opening of the injection tube.

[0205] By adjusting a series of operating conditions, microhelices with adjustable pitch (400~700 μm), diameter (100~250 μm), amplitude (600~1000 μm), and frequency (15~30 Hz) were prepared, all exhibiting good helical morphology (e.g., Figure 15 (As shown in diagrams a~c). In diagram a, when u o When the velocity is 0.0065, 0.0085, 0.0105, 0.0124 m / s, the pitch of the microhelix is ​​372, 458, 541, 656 μm; in Figure b, when D i When the microhelices are 60, 80, 100, and 110 μm, their diameters are 138, 174, 195, and 229 μm; in figure c, when... D i When the microhelix is ​​80, 90, 100, 110 μm, the amplitude of the microhelix is ​​754, 815, 881, 970 μm.

[0206] It is worth noting that low-concentration PEGDA undergoes volume shrinkage during photopolymerization (generally around 10%), resulting in a slight reduction in the volume of the microspirals. However, this phenomenon has little impact on the microspiral flow and the microspiral preparation process. Comparing the dimensionless prediction formulas shown in equations (I) to (IV) with the structural characteristics of the prepared microspirals, the results show that the prediction formulas have good consistency. The prediction errors are controlled within ±5%, 0 to -15%, +8% to -6%, and +10% to 0 for pitch, diameter, amplitude, and frequency, respectively (see [reference]). Figure 15(d~g figure). Among them, the volume shrinkage of the microspiral has a more significant impact on the small-scale diameter characteristics, and the diameter prediction error is significantly shifted downward (0~-15%, see d~g figure) due to the size effect. Figure 15 (See Figure e). Appropriately increasing the designed diameter value can effectively eliminate this effect. The method described in this invention allows for the efficient and controllable fabrication of microhelices. Furthermore, the mechanical strength of the microhelices can be precisely adjusted by changing the PEGDA content to meet the diverse application requirements of tissue culture and sensing devices.

Claims

1. A method for constructing a micro-helical flow, characterized in that, Includes the following steps: (1) Prepare internal phase fluid and external phase fluid Preparation of internal phase fluid: Dissolve a water-soluble polymer compound in water or glycerol to obtain an internal phase fluid; or dissolve or fully disperse a water-soluble polymer compound, a water-soluble photopolymerizable polymer monomer, and a photoinitiator in water or glycerol to obtain an internal phase fluid; Preparation of external phase fluid: Water is used as the external phase fluid; Alternatively, glycerol can be dissolved in water to obtain an external phase fluid; The viscosity of the internal phase fluid is controlled to be 50~1000 mPa·s, and the viscosity of the external phase fluid is controlled to be 1~20 mPa·s; the viscosity ratio of the internal phase fluid to the external phase fluid is controlled to be (50~1000):

1. (2) Constructing micro-spiral flow A micro-spiral flow is constructed using a primary microfluidic device, which includes an injection tube, a receiving tube, and a connecting tube. The outlet of the injection tube is tapered and is inserted into the inlet of the receiving tube. The injection tube and the receiving tube are connected by the connecting tube, and the injection tube, connecting tube, and receiving tube are arranged coaxially. The primary microfluidic device is arranged vertically, with the injection tube above the receiving tube. A receiving container filled with receiving liquid is placed below the receiving tube, with the outlet end of the receiving tube below the liquid surface of the receiving container. The receiving liquid is water. The inner phase fluid and the outer phase fluid are continuously injected into the injection tube and the receiving tube respectively using a constant flow injection pump. The inner phase fluid jets and expands into the receiving tube from the conical opening of the injection tube. After entering the receiving tube, the expansion of the inner phase fluid slows down and forms a coaxial laminar flow with the outer phase fluid. Under the action of the fluid rope effect, the inner phase fluid becomes unstable and coils due to buckling instability, forming a continuous and stable micro-spiral flow in the receiving tube. In this step, the ratio of the flow rate of the inner phase fluid to the flow rate of the outer phase fluid is controlled to be (10~150):

1.

2. The method for constructing micro-helical flow according to claim 1, characterized in that, The water-soluble polymeric compounds include sodium alginate, polyvinyl alcohol, chitosan, sodium carboxymethyl cellulose, or hydroxypropyl methyl cellulose; the water-soluble photopolymerizable polymeric monomers include polyethylene glycol dimethacrylate, methacrylic hydrogel, or N-isopropylacrylamide.

3. The method for constructing micro-helical flow according to claim 1, characterized in that, Replace the internal phase fluid and external phase fluid in step (1) with the internal phase fluid and external phase fluid prepared by the following method; Preparation of internal phase fluid: Use oil-soluble liquid as internal phase fluid; Alternatively, oil-soluble photopolymerizable polymer monomers and photoinitiators can be dissolved or fully dispersed in an oil-soluble liquid to obtain an internal phase fluid; Alternatively, oil-soluble photopolymerizable polymer monomers, photoinitiators, and oil-soluble liquids can be dissolved or fully dispersed in an oil phase solvent to obtain an internal phase fluid; Preparation of external phase fluid: using oil phase solvent as external phase fluid; Alternatively, the oil-soluble liquid can be dissolved in an oil-phase solvent to obtain an external phase fluid; The viscosity of the oil phase solvent is 1~10 mPa·s; the viscosity of the internal phase fluid is controlled to be 50~1000 mPa·s, and the viscosity of the external phase fluid is controlled to be 1~20 mPa·s; the ratio of the viscosity of the internal phase fluid to the viscosity of the external phase fluid is controlled to be (50~1000):

1.

4. The method for constructing micro-helical flow according to claim 3, characterized in that, The oil-soluble liquid includes silicone oil, polydimethylsiloxane, or polyglycerol ricinoleate; the oil-soluble photopolymerizable polymer monomer includes ethoxylated trimethylolpropane triacrylate or photosensitive resin; the oil phase solvent includes silicone oil, methyl oil, or soybean oil.

5. The method for constructing a micro-helical flow according to any one of claims 1 to 4, characterized in that, In step (2), the flow velocity of the inner phase fluid is controlled to be 0.1~0.5 m / s, and the flow velocity of the outer phase fluid is controlled to be 0.001~0.015 m / s.

6. The method for constructing a micro-helical flow according to any one of claims 1 to 4, characterized in that, The inner diameter of the conical opening of the injection tube of the first-stage microfluidic device in step (2) is 60~130 μm.

7. The method for constructing a micro-helical flow according to any one of claims 1 to 4, characterized in that, The inner diameter of the receiving tube of the first-stage microfluidic device in step (2) is 700~1500 μm.

8. A method for precise control of the structural characteristics of a micro-helical flow, characterized in that, The micro-spiral flow is constructed using the method described in any one of claims 1 to 7. During the construction of the micro-spiral flow, one or more of the following factors can be adjusted: the viscosity of the inner phase fluid, the viscosity of the outer phase fluid, the inner diameter of the conical opening of the injection tube, the inner diameter of the receiving tube, the flow rate of the inner phase fluid, and the flow rate of the outer phase fluid. This adjustment can be made to adjust the pitch, diameter, amplitude, and frequency of the micro-spiral flow constructed in step (2).

9. The method for precise control of the micro-helical flow structure characteristics according to claim 8, characterized in that, During the construction of the micro-spiral flow, the pitch of the micro-spiral flow is positively linearly related to the flow velocity of the external phase fluid, and the pitch of the micro-spiral flow can be controlled and adjusted based on this relationship; the diameter of the micro-spiral flow is positively linearly related to the inner diameter of the conical opening of the injection tube, and the diameter of the micro-spiral flow can be controlled and adjusted based on this relationship; when the edge of the micro-spiral flow is in contact with the inner wall of the receiving tube, the amplitude of the micro-spiral flow is controlled by the inner diameter of the receiving tube, and the amplitude of the micro-spiral flow can be increased by increasing the inner diameter of the receiving tube; the frequency of the micro-spiral flow is positively linearly related to the flow velocity of the internal phase fluid, and the frequency of the micro-spiral flow can be controlled and adjusted based on this relationship.

10. A method for predicting the structural characteristics of micro-helical flow, characterized in that, The pitch, diameter, amplitude, and frequency of the micro-spiral flow constructed using the method described in any one of claims 1 to 7 can be predicted based on the relationships shown in equations (I) to (IV). Equation (I) Equation (II) Equation (III) Formula (IV) In equations (I) to (IV), P , D , A , Ω These represent the pitch, diameter, amplitude, and frequency of the micro-spiral flow, respectively. D i , D o These are the inner diameters of the conical tip of the injection tube and the inner diameter of the receiving tube of the primary microfluidic device, respectively. u i , u o The flow velocities of the internal and external phase fluids are separated. μ i , μ o The viscosity of the internal phase fluid and the external phase fluid, respectively.

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