Method for preparing biocompatible microscrews and microscrew scaffolds with controllable structure based on non-confined microfluidics

Abstract

This invention belongs to the field of microspiral functional material preparation technology, and provides a method for preparing structurally controllable biocompatible microspirals and microspiral scaffolds based on unconfined microfluidics. The method for preparing microspirals includes the following steps: (1) preparing an inner phase solution and a receiving liquid; (2) vertically arranging the injection tube so that the outlet end is below the inlet end, placing a collection container filled with the receiving liquid below the receiving tube so that the outlet end of the injection tube is below the surface of the receiving liquid; injecting the inner phase solution into the injection tube, the inner phase solution is squeezed out from the conical opening of the injection tube and expands into the receiving liquid, forming a continuous and stable microspiral flow in the receiving liquid; applying ultraviolet light to the collection container to solidify the microspiral flow to obtain the microspiral. This invention can improve the structural controllability of microspirals, realize micron-millimeter cross-scale control of microspiral structures, and reduce the risk of device blockage. This invention can also improve the preparation efficiency of microspiral scaffolds.

Description

Technical Field

[0001] This invention belongs to the field of microhelical functional material preparation technology, and relates to a method for preparing biocompatible microhelices and microhelical scaffolds with controllable structures based on unconfined microfluidics. Background Technology

[0002] Microhelical functional materials, due to their excellent material properties and unique three-dimensional structure, have been applied in important fields such as mechanical engineering, materials engineering, and tissue engineering, attracting the attention and research of many scholars. In mechanical engineering, microhelical functional materials are often used as basic units for microsprings, actuators, or sensors. Utilizing their reversible elastic deformation and unique mechanical response characteristics, they can efficiently realize energy storage, conversion, and transfer. In materials engineering, microhelical functional materials are used to construct anisotropic composite materials, flexible devices, or supermaterials, endowing them with mechanical, electrical, or optical properties not possessed by traditional materials. In tissue engineering, microhelical functional materials exhibit even more unique application value. Their structure can highly mimic the helical or wavy arrangement of components such as collagen fibers and elastin in the natural extracellular matrix, thus providing cells with a key medium to guide their adhesion, spreading, directional migration, and even functional differentiation. They are ideal building blocks for constructing biomimetic tissue scaffolds (ACS Appl. Mater. Interfaces 2025, 17(51): 70059-70070). The performance of microhelical functional materials is determined by their material properties and structural features (such as pitch, diameter, amplitude, etc.). The structural features of microhelical functional materials directly affect their mechanical properties, specific surface area, permeability, and interfacial properties with cells, thus having a decisive impact on the biological efficacy of the microhelical scaffolds prepared from them. For example, microhelical functional materials with smaller pitches, due to their tighter helical structure, usually exhibit higher three-dimensional structural stiffness and energy storage density, making them suitable for scenarios requiring stable mechanical support or guiding the tight arrangement of cells, such as tendon or ligament repair. At the same time, the batch construction of structurally controllable microhelical functional materials is the key to the preparation of microhelical scaffolds. The preparation of microhelical scaffolds often requires a large amount of microhelical functional materials, and it takes several hours to prepare meter-length microhelical functional materials in a single microfluidic chip, resulting in low preparation efficiency. In addition, practical applications also place strict requirements on the uniformity of microhelical functional materials (Adv. FiberMater. 2023, 6(1): 68-105). Therefore, the efficient preparation of microhelical functional materials with controllable structures is of great significance for improving the performance and preparation efficiency of microhelical scaffolds.

[0003] Currently, researchers have developed various microfluidic strategies to prepare microhelical functional materials, including solvent exchange and ionic crosslinking. These strategies are all based on the fluid rope effect caused by rapid phase transitions due to solute precipitation or a sudden increase in viscosity due to crosslinking reactions, which constructs microhelical flows. Further solidification yields microhelical functional materials. In the solvent exchange method, Liu et al. (Angew. Chem. Int. Ed. 2021, 60(47): 25089-25096) prepared PCL microhelical functional materials with good mechanical properties using a formic acid (FA) solution of polycaprolactone (PCL) and deionized water. They further controlled the structural characteristics of the microhelical functional materials by adjusting the gravitational component changes caused by adjusting the device tilt angle. This strategy requires a fast phase transformation rate in the prepolymer, thus limiting the wide selection of solution systems. Simultaneously, the introduction of gravity increases the complexity of the microfluidic system, reduces stability, and is unsuitable for large-scale preparation. Ionic crosslinking is the mainstream method for preparing microhelical functional materials, mainly using the sodium alginate (NaAlg)-calcium chloride (CaCl2) system. Shao et al. (Adv. Healthc. Mater. 2019, 8(9): 1900014) prepared CaAlg / GelMA microhelical functional materials using an aqueous solution of methacryloyl gelatin (GelMA) and CaCl2 with NaAlg solution based on the phase inversion method, and dynamically constructed microhelical scaffolds with diverse structures using 3D printing. This strategy helps to accurately prepare microhelical functional materials with specific structures and functions, but it requires expensive equipment and complex systems, which is not conducive to widespread application. Ma et al. (J. Polym. Sci. 2022, 60(11):1741-1749) used a conical jacket design to enhance focused flow and prepare large quantities of CaAlg microhelical functional materials, and then prepared microhelical scaffolds by orderly arranging the microhelical functional materials on a polyacrylamide (PAM) substrate. This strategy reduces the risk of online channel blockage in CaAlg gels to some extent, but the in-situ gel generation method is still significantly affected by flow conditions and external fluctuations, resulting in low system robustness. In particular, the batch preparation of microhelical functional materials generally requires arrayed capillary conical designs, but traditional capillary devices have low fabrication efficiency, and damage to a single conical conical can greatly affect system stability. While easily fabricated PDMS devices face the problem of not being able to smoothly discharge large amounts of product in real time. Therefore, the simple and efficient preparation of structurally controllable microhelical functional materials in microfluidic devices remains a significant challenge. Summary of the Invention

[0004] To address the problems of online clogging, process redundancy, and difficulty in structural adjustment in the preparation of microhelices in existing technologies, as well as the low efficiency in the preparation of microhelical scaffolds, this invention provides a method for preparing structurally controllable biocompatible microhelices and microhelical scaffolds based on unrestricted microfluidics. This method improves the structural controllability of microhelices, enables micron- to millimeter-scale control of microhelical structures, reduces the risk of microfluidic device clogging during microhelice preparation, and improves the preparation efficiency of microhelical scaffolds.

[0005] To achieve the above-mentioned objectives, the technical concept of this invention is mainly as follows: First, a high-viscosity internal phase solution is directly injected into a low-viscosity receiving liquid through the injection tube of a microfluidic device. By adjusting the operating conditions such as the viscosity of the internal phase solution, the flow rate, the outlet inner diameter of the injection tube, and the viscosity of the receiving liquid, a simple construction of a micro-spiral flow is achieved based on the fluid rope effect caused by the phase viscosity difference. Then, the micro-spiral flow is polymerized online using ultraviolet light to achieve controllable preparation of the micro-spiral. Finally, a rotating plate is set in the receiving liquid, and the ends of the micro-spirals are fixed on the rotating plate. The rotation of the rotating plate is used to achieve orderly winding of the micro-spirals on the rotating plate. The rotating plate with completed micro-spiral winding is placed in a casting mold, poured into the casting liquid, and irradiated with ultraviolet light to solidify and obtain a hydrogel. The hydrogel is cut or trimmed to achieve efficient preparation of the micro-spiral scaffold.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing structurally controllable biocompatible microhelices based on unconfined microfluidics includes the following steps:

[0008] (1) Preparation of two-phase solution

[0009] A prepolymer solution is obtained by dissolving a water-soluble photopolymerizable polymer monomer, a photoinitiator, and a surfactant in deionized water. An internal phase solution is obtained by dissolving a water-soluble polymer compound in the prepolymer solution. The viscosity of the internal phase solution is 500~1000 mPa·s.

[0010] Deionized water is used as the receiving liquid; or a water-soluble polymer compound is dissolved in deionized water to obtain the receiving liquid; the viscosity of the receiving liquid is 10~20 mPa·s;

[0011] (2) Preparation of microhelices

[0012] A microfluidic device is used to construct a micro-spiral flow. The microfluidic device includes an injection tube with a conical outlet. The microfluidic device is arranged vertically so that the outlet end of the injection tube is below the inlet end. A collection container filled with receiving liquid is placed below the receiving tube so that the outlet end of the injection tube is below the liquid surface of the receiving liquid.

[0013] The internal phase solution is injected into the injection tube using a syringe pump. The internal phase solution is squeezed out from the conical opening of the injection tube and expands into the receiving liquid. Under the action of the fluid rope effect, the internal phase solution becomes unstable due to buckling instability and coils in an orderly manner in the receiving liquid to form a continuous and stable micro-spiral flow.

[0014] Applying ultraviolet light to a position in the collection container where the micro-spiral flow morphology has reached a stable state triggers a photopolymerization reaction of the photopolymerizable polymer monomers in the micro-spiral flow, resulting in micro-spirals.

[0015] In step (2) of the above-mentioned method for preparing microspirals, it is preferable to control the outlet inner diameter of the injection tube of the microfluidic device to be 60~200 μm.

[0016] In step (2) of the above-mentioned method for preparing microspirals, it is preferable to control the flow rate of the inner phase solution to be 0.01~0.50 m / s.

[0017] In step (1) of the above-mentioned method for preparing microspirals, the role of the water-soluble photopolymerizable polymer monomer is to solidify the microspiral flow into a microspiral after the photoinitiation reaction. The water-soluble photopolymerizable polymer monomer can be selected according to the actual application requirements. For example, feasible water-soluble photopolymerizable polymer monomers include polyethylene glycol diacrylate (PEGDA), polyethylene glycol monoacrylate (PEGMA), hyaluronic acid methacrylate (HAMA), or alginate methacrylate (AlgMA). However, feasible water-soluble photopolymerizable polymer monomers are not limited to the specific types of water-soluble photopolymerizable polymer monomers listed above.

[0018] In step (1) of the above-mentioned method for preparing microspirals, the role of the water-soluble polymer compound is to adjust the viscosity of the inner phase solution. The water-soluble polymer compound can be selected according to the structural preparation requirements of the microspiral flow. For example, feasible water-soluble polymer compounds include sodium alginate (NaAlg), xanthan gum (XG), methyl cellulose (MC), or polyethylene glycol (PEG). However, feasible water-soluble polymer compounds are not limited to the specific types of polymer compounds listed above.

[0019] In step (1) of the above-mentioned method for preparing microspirals, the role of the photoinitiator is to initiate the photopolymerization reaction of water-soluble photopolymerizable polymer monomers under ultraviolet light to achieve the transformation from microspiral flow to microspiral. The photoinitiator can be selected according to the reaction conditions of the water-soluble photopolymerizable polymer monomers. For example, feasible photoinitiators include Irgacure 2959, LAP, Na / Li-TPO or Na / Li-BAPO, but feasible photoinitiators are not limited to the specific types of photoinitiators listed above.

[0020] In step (1) of the above-mentioned method for preparing microspirals, the role of the surfactant is to stably disperse the emulsion of water-soluble photopolymerizable polymer monomers in water. The surfactant can be selected according to the chemical properties of the water-soluble photopolymerizable polymer monomers. For example, feasible surfactants include F127, Poloxamer 188, EL-40 or mPEG-C12, but feasible surfactants are not limited to the specific types of surfactants listed above.

[0021] In step (1) of the above-described method for preparing microspirals, to impart certain functions to the microspirals, the inner phase solution may also contain functional materials, including magnetically responsive materials, temperature-responsive materials, or pH-responsive materials. The specific type and amount of functional materials can be selected according to actual application requirements. For example, to impart magnetic responsiveness to the microspirals, Fe3O4 nanoparticles can be added to the inner phase solution; to impart temperature responsiveness to the microspirals, N-isopropylacrylamide (PNIPAm) can be added to the inner phase solution; to impart pH responsiveness to the microspirals, polymethyl methacrylate (PMAA) can be added to the inner phase solution. Typically, the mass fraction of the functional material in the inner phase solution is 1% to 10%.

[0022] In step (1) of the above-mentioned method for preparing microspirals, in order to clearly observe the flow process and micromorphology of the microspiral flow, the inner phase solution may also contain water-soluble dyes. For example, feasible water-soluble dyes include Rhodamine B, Neutral Red, Congo Red, etc.

[0023] In step (1) of the above-mentioned method for preparing microspirals, the mass fraction of water-soluble photopolymerizable polymer monomers in the inner phase solution is usually 10%~20%, the mass fraction of photoinitiator is usually 1%~2%, the mass fraction of surfactant is usually 1%~2%, and the mass fraction of water-soluble polymer compound is usually 0.1%~2.5%.

[0024] In the above-mentioned method for preparing microspirals, one or more structural features of the microspiral, such as pitch, diameter, amplitude, and frequency, can be controllably adjusted by adjusting one or more operating conditions, including the viscosity of the inner phase solution, flow rate, outlet inner diameter of the injection tube, and viscosity of the receiving liquid.

[0025] This invention also provides a method for preparing biocompatible microspiral scaffolds, comprising the following steps:

[0026] (1) Preparation of casting liquid

[0027] The casting solution is obtained by dissolving water-soluble photopolymerizable polymer monomers and photoinitiators in deionized water;

[0028] (2) Preparation of microhelices

[0029] Microhelices were prepared using the method described above.

[0030] (3) Fabrication of microspiral scaffolds

[0031] Place the rotating plate in the receiving liquid of the collection container, and fix the end of the microspiral in the groove of the rectangular plate of the rotating plate. Control the rectangular plate of the rotating plate to rotate around its own axis, and wind the microspiral in an orderly manner around the rectangular plate. Take out the rotating plate after the microspiral is wound, place it in the casting mold, add casting liquid to the casting mold to completely immerse the microspiral, apply ultraviolet light to irradiate until the casting liquid turns into hydrogel, cut or cut the hydrogel to break the connection between the hydrogel and the rotating plate, remove the rotating plate, and obtain the microspiral support.

[0032] The rotating plate is a rectangular plate with grooves on its surface for fixing micro-spirals. A connecting shaft is provided on the rectangular plate, and the rectangular plate is driven to rotate around its own axis by a rotating mechanism.

[0033] In the above-described method for preparing microspiral scaffolds, the polymer monomer is a water-soluble photopolymerizable polymer monomer. For example, feasible water-soluble photopolymerizable polymer monomers include polyethylene glycol diacrylate (PEGDA), polyethylene glycol monoacrylate (PEGMA), hyaluronic acid methacrylate (HAMA), alginate methacrylate (AlgMA), or acrylamide (AM). However, feasible water-soluble photopolymerizable polymer monomers are not limited to the specific types listed above. The polymer monomer may be the same as or different from the water-soluble photopolymerizable polymer monomer used in preparing the microspiral scaffold.

[0034] In the above-mentioned method for preparing microspiral scaffolds, the crosslinking agent is a crosslinking agent that can undergo free radical copolymerization and crosslinking reaction with polymer monomers. The specific crosslinking agent can be selected according to the actual application requirements, such as acrylamide crosslinking agents, acrylic acid / methacrylic acid bifunctional crosslinking agents, etc.

[0035] In the above-mentioned method for preparing microspiral scaffolds, the mass fraction of the polymer monomer in the casting liquid is 10%~20%, the mass fraction of the chemical crosslinking agent is 0.1%~0.2%, and the mass fraction of the photoinitiator is 0.1%~0.2%.

[0036] In the above-described method for preparing microspiral scaffolds, the connecting shaft on the rectangular plate is connected to a driving mechanism, and the rectangular plate is driven to rotate around its own axis by a rotating mechanism. The driving mechanism can be a constant-speed motor.

[0037] In the above-mentioned method for preparing microspiral scaffolds, step (3) should control the rotation speed of the rectangular plate of the rotating plate around its own axis to match the generation speed of the microspiral in step (2), so as to avoid stretching, deforming or damaging the microspiral formed in step (2). Generally, the length of the microspiral corresponding to the rectangular plate completing one rotation is the perimeter of the rectangular plate. The length of the microspiral can be calculated by multiplying the time required for the rectangular plate to complete one rotation by the frequency and pitch of the microspiral.

[0038] In the above-mentioned method for preparing microspiral scaffolds, the mechanical properties of the prepared microspiral scaffolds can be controlled by adjusting the number and / or structure of the microspirals.

[0039] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0040] 1. This invention provides a method for preparing structurally controllable biocompatible microhelices based on unconfined microfluidics. The method involves directly injecting a high-viscosity internal phase solution into a low-viscosity receiving liquid through the injection tube of a microfluidic device. By adjusting the viscosity, flow rate, outlet diameter of the injection tube, and viscosity of the receiving liquid, the microhelical flow is easily constructed based on the fluid rope effect induced by the phase viscosity difference. After the microhelical flow is constructed, it is polymerized online using ultraviolet light, thus achieving controllable preparation of the microhelices. In this method, the microhelical construction process does not involve cross-linking reactions or phase transitions, solving the problems of online clogging and process redundancy in traditional microhelical construction methods. The main body of the microfluidic device used is an injection tube with a conical outlet, which has a simple structure, significantly reducing the complexity of the microfluidic system and effectively improving the simplicity and stability of the microhelical construction process.

[0041] A high-viscosity internal phase solution is directly injected into a low-viscosity receiving liquid through the injection tube of a microfluidic device. By adjusting the operating conditions such as the viscosity of the internal phase solution, the flow rate, the outlet inner diameter of the injection tube, and the viscosity of the receiving liquid, a simple micro-spiral flow is constructed based on the fluid rope effect caused by the phase viscosity difference. Then, the micro-spiral flow is polymerized online using ultraviolet light to achieve controllable preparation of micro-spirals. Finally, a rotatable rotating plate is placed in the receiving liquid, and the ends of the micro-spirals are fixed on the rotating plate. The rotation of the rotating plate achieves orderly winding of the micro-spirals on the rotating plate. The rotating plate with completed micro-spiral winding is placed in a casting mold, poured into the casting liquid, and irradiated with ultraviolet light to solidify and obtain a hydrogel. The hydrogel is then cut or trimmed to achieve efficient preparation of the micro-spiral scaffold.

[0042] 2. The method for preparing biocompatible microhelices with controllable structures based on unrestricted microfluidics described in this invention uses ultraviolet light to polymerize the microhelical flow formed online, achieving in-situ generation of microhelices. The millisecond-level ultraviolet curing reaction enables rapid shaping of the microhelical flow while completely preserving the preset structural features of the microhelical flow. The microgel formed by ultraviolet curing at a location far from the injection tube outlet does not cause injection tube blockage, effectively improving the controllability and stability of the microhelice preparation process.

[0043] 3. The method for preparing structurally controllable biocompatible microhelices based on unrestricted microfluidics described in this invention has significant advantages in preparing microhelices across scales. By adjusting microfluidic operating parameters, the pitch, amplitude, and diameter of the microhelices can be controlled over a large scale range. For example, this invention achieves micrometer-to-millimeter scale control of microhelical dimensions simply by adjusting the inner diameter of the injection tube outlet, i.e., within a pitch range of 0.4–3.7 mm, a diameter range of 0.17–0.55 mm, and an amplitude range of 0.7–2.7 μm. Furthermore, the prepared microhelices all exhibit excellent helical morphology and good dimensional uniformity. This indicates that the method of this invention can better meet the requirements of different application scenarios for microhelical scale.

[0044] 4. Based on the method for preparing microhelices described in this invention, this invention also provides a method for preparing a biocompatible microhelical scaffold. This method involves placing a rotating plate in a receiving liquid during the microhelical preparation process, fixing the ends of the microhelices to the rotating plate, and using the rotation of the rotating plate to achieve orderly winding of the microhelices. The rotating plate with completed microhelical winding is placed in a casting mold, filled with casting liquid, and cured by ultraviolet light to obtain a hydrogel. The hydrogel is then cut or trimmed to achieve efficient preparation of the microhelical scaffold. In this microhelical scaffold preparation process, the rotation of the rotating plate is driven by a rotating mechanism, achieving orderly winding of the microhelices on the rotating plate. This process does not rely on manual operation, improving the efficiency and accuracy of the orderly arrangement of microhelices. Furthermore, this process does not require high-performance printing equipment, effectively improving the preparation efficiency of the microhelical scaffold and reducing preparation costs. Attached Figure Description

[0045] Figure 1 This invention provides schematic diagrams of the preparation of microhelices and microhelical scaffolds. Figure a is a global view of the microfluidic system constructing a polyethylene glycol diacrylate (PEGDA) / sodium alginate (NaAlg) microhelical flow; Figure b is a schematic diagram of the microhelical flow structural characteristics; and Figure c is a schematic diagram of the microhelical scaffold preparation process. In the figures, μ... i For internal phase viscosity, u i Let μ be the internal phase flow velocity. o D is the external phase viscosity. iP is the inner diameter of the injection tube outlet, D is the pitch, A is the amplitude, and Ω is the frequency.

[0046] Figure 2 These are the rheological characteristics of the two-phase solution. Figure a shows the viscosity of the inner phase solution as a function of NaAlg concentration, and Figure b shows the viscosity of the receiving liquid as a function of CMC concentration.

[0047] Figure 3 These are optical photographs of the flow regime distribution and morphology regulation of microfluidics. Image a shows the microfluidics exhibiting jet, helical, and turbulent flow regimes. Image b shows the change in micro-helical flow morphology with increasing internal phase solution flow rate. (μ...) i = 826mPa·s, Di = 120 μm, μ o = 2.5 mPa·s, the arrow represents the flow rate of the internal phase solution, and the flow rate unit is μL / min.

[0048] Figure 4 The effects of the internal phase solution flow rate and the inner diameter of the injection tube outlet on the pitch of the micro-spiral flow are shown in Figures a-b. Figures a-b show the optical morphology and pitch variation of the micro-spiral flow under different internal phase flow rates, while Figures c-d show the optical morphology c and pitch variation d of the micro-spiral flow under different injection tube outlet inner diameters. The legends are the inner diameter of the injection tube outlet (Figure b, μm) and the internal phase solution flow rate (Figure d, m / s), respectively.

[0049] Figure 5 The figures show the effects of other operating conditions on the pitch of the micro-spiral flow. Figures a and b show the optical morphology (a) and pitch variation (b) of the micro-spiral flow under different internal phase solution viscosities. Figures c and d show the optical morphology (c) and pitch variation (d) of the micro-spiral flow under different receiving liquid viscosities. The legend represents the flow rate of the internal phase solution (Figures b and d, m / s).

[0050] Figure 6 This describes the evolution and stability characteristics of the pitch in a micro-spiral flow. Figure a shows the pitch development along the direction of gravity, and Figure b shows the temporal development of the first formed pitch. (The text then repeats the last two characters, u, which doesn't need to be translated but can be left as is.) i = 0.147 m / s, D i = 120 μm, μ i = 826 mPa·s, μ o = 3.3 mPa·s.

[0051] Figure 7 The diagram shows the effect of operating conditions on the diameter of the micro-spiral flow. Figures a to d show the adjustment of the micro-spiral flow diameter under different internal phase solution flow rates, injection tube outlet inner diameters, internal phase solution viscosities, and receiver liquid viscosities. The legends are the injection tube outlet inner diameter (Figure a, μm) and the internal phase solution flow rate (Figures b to d, m / s), respectively.

[0052] Figure 8 The influence of operating conditions on the amplitude of the micro-spiral flow is shown in Figures a to d. Figures a to d show the control of the micro-spiral flow amplitude under different internal phase solution flow rates, injection tube outlet inner diameters, internal phase solution viscosities, and receiver liquid viscosities. The legends are the injection tube outlet inner diameter (Figure a, μm) and the internal phase solution flow rate (Figures b to d, m / s), respectively.

[0053] Figure 9 The influence of operating conditions on the frequency of the micro-spiral flow is shown in Figures a to d. Figures a to d show the adjustment of the frequency of the micro-spiral flow under different internal phase solution flow rates, injection tube outlet inner diameters, internal phase solution viscosities, and receiver liquid viscosities. The legends are the injection tube outlet inner diameter (Figure a, μm) and the internal phase solution flow rates (Figures b to d, m / s), respectively.

[0054] Figure 10 This is a frequency stability analysis of the microhelical flow. Figures a and b show the frequency variation of the microhelical flow over time when the inner diameter of the injection tube outlet is 100 μm and 120 μm, respectively. Where, u i = 0.085 m / s, μ i = 922 mPa·s, μ o = 3.3 mPa·s.

[0055] Figure 11 The figures show the predicted characteristics of the micro-spiral flow structure, with figures a to d showing the predicted pitch, diameter, amplitude, and frequency of the micro-spiral flow, respectively.

[0056] Figure 12 These are optical images of microhelices at different scales, where image a shows D... i = 100 μm, P = 0.412, 0.392, 0.338, 0.314 mm, D in figure b i = 140 μm, P = 2.536, 2.145, 1.880, 1.773 mm, D in figure c i = 200 μm, P = 3.738, 3.381, 3.086, 2.959 mm.

[0057] Figure 13 This is the size distribution of the microhelix, where figures a~c represent the dimensions of pitch, amplitude, and diameter, respectively. Where u i = 0.130 m / s, μ i = 826 mPa·s, D i = 140 μm, μ o = 8.0 mPa·s.

[0058] Figure 14This involves dimensional analysis of microhelices at different scales, specifically D in figures a~c. i = 100 μm, 140 μm, 200 μm.

[0059] Figure 15 These are electron micrographs of microhelices with different structural morphologies. Images a to e are macroscopic images of the microhelices with a scale bar of 200 μm, while images f to h are microscopic images of the microhelices with a scale bar of 10 μm.

[0060] Figure 16 These are optical images of mass-produced microhelices. Images a-b show microhelices with and without Fe3O4 nanoparticles, while images c-d show mass-produced magnetic microhelical fibers. Ω = 7.1 Hz, P = 1.472 mm, and t... i =1500 s, L = 16 m.

[0061] Figure 17 These are optical images of the magnetic attraction behavior of the magnetic microhelix. Images a-b show the deformation behavior of the magnetic microhelix at 0 s and 8 s under the attraction of the magnet on the right.

[0062] Figure 18 Images a-b show optical images of a large number of fabricated microspirals and the microspirals arranged and wound in an orderly manner on a rotating plate. Figure 18 Images c~d are optical images of microspiral scaffolds fabricated using microspirals of different sizes.

[0063] Figure 19 These are the tensile test results of the micro-spiral scaffold. Figure a is an optical image of the tensile process, and Figure b is the stress curve.

[0064] Figure 20 The results show the mechanical properties of the micro-spiral scaffold. Figure a shows the stress-strain curves of the micro-spiral scaffold in different tensile directions, while figures b to d show the effects of tensile direction, number of micro-spirals, and micro-spiral amplitude on the Young's modulus of the micro-spiral scaffold. Detailed Implementation

[0065] The following examples further illustrate the method for preparing structurally controllable biocompatible microhelices and microhelical scaffolds based on the unrestricted microfluidic method provided by the present invention. It should be noted that the following examples are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present 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 the present invention.

[0066] In the following embodiments, the microfluidic device used is a single-nozzle device, which includes an injection tube and a fixing plate. The outlet end of the injection tube is tapered and fixed to the fixing plate. The outlet end of the injection tube extends out of the edge of the fixing plate. The injection tube is made of a cylindrical glass capillary tube, and the fixing plate is a glass slide. Fabrication process of the injection tube: One end of the cylindrical glass capillary tube is drawn into a tapered opening using a needle puller, and then polished on sandpaper until the inner diameter of the outlet is 60~200 μm. The outer diameter of the cylindrical section is 960 μm and the inner diameter is 700 μm. After polishing, it is placed in anhydrous ethanol and deionized water and ultrasonically vibrated for 60 s to remove impurities, and then dried with nitrogen for later use. The injection tube is inserted into the sintered plastic steel needle (the plastic steel needle is fitted onto the outside of the injection tube so that the two are arranged coaxially and the gap between them is sealed with AB glue). The plastic steel needle is glued and fixed to the glass slide, so that the tapered opening of the injection tube extends 2 cm out of the glass slide. The prepared single nozzle device is placed at room temperature to dry for 12 h for later use.

[0067] This single-nozzle device is used in conjunction with an injection pump and a UV point light source; a schematic diagram of the three components is shown below. Figure 1 As shown in Figure a, the inlet end of the plastic-coated steel needle is connected to the outlet end of the injection pump via a fitting (polyethylene tube). During use, the single-nozzle device is placed in the collection container with the injection tube perpendicular to the horizontal plane. The outlet end of the injection tube is 0.5–1 cm below the surface of the receiving liquid in the collection container. A UV point light source is positioned outside the collection container, below the outlet of the injection tube of the single-nozzle device. The light emitted by the UV point light source perpendicularly irradiates the microspiral flow exiting the injection tube outlet, thereby optically crosslinking and solidifying the microspiral flow to form microspirals. To facilitate the capture of optical images of the microspiral flow and microspirals, a high-speed camera is positioned on the outside of the collection container, opposite the UV point light source.

[0068] The following embodiments illustrate the process flow diagram for preparing microspirals. Figure 1As shown in Figure c, the tools used include a rotating plate and a casting mold. The rotating plate is a rectangular polystyrene (PS) plate of a certain thickness. A groove for fixing the micro-spiral is provided on the surface of the rectangular plate (at one edge of the rectangular plate). Connecting shafts are provided on opposite sides of the rectangular plate, and these shafts are connected to the rotating mechanism to drive the rectangular plate to rotate around its own axis, thereby evenly winding the micro-spiral around the rectangular plate. The casting mold is a rectangular cavity with an opening at the top (the overall shape is a regular rectangular cavity with a flat bottom and side walls perpendicular to the bottom, forming a shallow groove-like mold cavity), made of polymethyl methacrylate (PMMA). First, the rotating plate is fixed in the receiving liquid of the collection container. The connecting shaft of the rotating plate is connected to a rotating mechanism (such as a constant speed motor) located outside the collection container. Then, the end of the micro-spiral is clamped into the groove of the rectangular plate of the rotating plate to achieve fixation. Then, the rotating mechanism drives the rectangular plate to rotate slowly around its own axis to achieve orderly winding and arrangement of the micro-spiral on the rectangular plate. After that, the rotating plate with completed micro-spiral winding is taken out and placed in a casting mold. Casting liquid is added to the casting mold to completely immerse the micro-spiral. Ultraviolet light is applied to the casting mold to induce the photopolymerization of the photopolymerizable polymer monomers in the casting liquid to undergo a photopolymerization reaction, which solidifies the casting liquid to obtain hydrogel. Finally, the hydrogel is cut or trimmed to disconnect the hydrogel from the rotating plate. The rotating plate is then removed to obtain the micro-spiral support.

[0069] Example 1

[0070] In this embodiment, a method for preparing structurally controllable microhelical flows based on unconfined microfluidics is provided, and the steps are as follows:

[0071] (1) Preparation of two-phase solution

[0072] Polyethylene glycol diacrylate (PEGDA), 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (Irgacure 2959), poloxamer 407 (F127), and rhodamine B were dissolved in deionized water to obtain a prepolymer solution. Sodium alginate (NaAlg) was dissolved in the prepolymer solution to obtain an inner phase solution. This step prepared inner phase solutions of different concentrations. In the inner phase solutions, the mass fraction of PEGDA was 10%~20%, the mass fraction of Irgacure 2959 was 1%~2%, the mass fraction of F127 was 1%, the mass fraction of Rhodamine B was 0.1%, and the mass fraction of NaAlg was 0.1%~2.5%.

[0073] Sodium carboxymethyl cellulose (CMC) was dissolved in deionized water to prepare a receiving solution; different concentrations of receiving solutions were prepared in this step, and the mass fraction of CMC in the receiving solution was 0%~0.5%.

[0074] The viscosity of internal phase solutions and receiving liquids of different concentrations was tested using a rheometer.

[0075] (2) Constructing micro-spiral flow

[0076] A micro-spiral flow is constructed using a single nozzle device with the structure described above as a microfluidic device.

[0077] Arrange the single nozzle device vertically so that the outlet end of the injection tube is below the inlet end. Place a collection container containing the receiving liquid below the receiving tube, so that the outlet end of the injection tube is a fixed distance (1 cm) below the liquid surface of the receiving liquid. The collection container is made of quartz glass.

[0078] The internal phase solution is injected into the injection tube using a constant flow syringe pump. The internal phase solution is squeezed out from the conical opening of the injection tube and expands into the receiving liquid. Under the action of the fluid rope effect, the internal phase solution becomes unstable due to buckling instability and forms a continuous and stable micro-spiral flow in the receiving liquid.

[0079] To investigate the effect of the inner phase solution flow rate on the construction of the microspiral flow, the inner phase solution flow rate was adjusted to control the inner phase solution flow rate within the range of 0.01–0.50 m / s. To investigate the effect of the injection tube outlet inner diameter on the construction of the microspiral flow, injection tubes with different outlet inner diameters were prepared, with the outlet inner diameter controlled within the range of 60–200 μm. To investigate the effect of the inner phase solution viscosity on the construction of the microspiral flow, the inner phase solution viscosity was adjusted by regulating the mass fraction of NaAlg in the inner phase solution, with the viscosity controlled within the range of 500–1000 mPa·s. To investigate the effect of the receiving liquid viscosity on the construction of the microspiral flow, the receiving liquid viscosity was adjusted by regulating the mass fraction of CMC in the receiving liquid, with the viscosity controlled within the range of 1–20 mPa·s.

[0080] To investigate the morphological characteristics of micro-spiral flows in the axial direction, images of the micro-spiral flows at different times were taken, and the pitch distribution in the axial direction and the frequency distribution during the forming process were analyzed. To further investigate the stability of the micro-spiral flow forming process, the frequencies of two typical operating conditions were recorded, and the influence of operating condition changes on the frequency distribution was analyzed. To analyze the influence of operating conditions on the structural characteristics of micro-spiral flows and to establish a guiding framework for constructing target micro-spiral flows, the "operating condition-structural characteristics" database was dimensionless and custom-fitted, and correlations were established for the pitch, diameter, amplitude, and frequency structural characteristics of micro-spiral flows.

[0081] The viscosity of the two-phase solution has a significant impact on the construction effect of the microhelical flow. With increasing NaAlg concentration, the viscosity of the inner phase solution exhibits a power-law increasing trend (e.g., ...). Figure 2 As shown in Figure a), the viscosity of the receiving liquid increases linearly with increasing CMC concentration (e.g., ...). Figure 2 (As shown in Figure b). The microfluidic morphology is quite sensitive to changes in the viscosity of the receiving liquid, so a linearly tunable external phase viscosity relationship makes it easy to construct a stable solution environment.

[0082] In a typical experiment, as the internal phase solution flow rate (Q) increases... i As the flow rate increases, the microfluidic fluid successively exhibits jet, spiral, and turbulent flow patterns (such as...). Figure 3 As shown in Figure a). At low internal phase solution flow rates, the microfluidic fluid settles naturally along the direction of gravity; at medium internal phase solution flow rates, the microfluidic fluid forms a coiled structure due to its inability to release kinetic energy in time, exhibiting excellent helical morphology; at high internal phase solution flow rates, the microfluidic fluid accumulates continuously due to its low settling velocity, which cannot provide space for newly generated micro-helical flows, thus affecting the spatial flow field and forming turbulence. Subsequently, the global morphology of the micro-helical flow was controlled. When the internal phase solution flow rate was between 120 and 360 μL / min, the formed microfluidics all exhibited excellent helical morphology (e.g., ...). Figure 3 (As shown in Figure b).

[0083] By comprehensively adjusting the viscosity (μ) of the internal phase solution i ), Inner diameter of injection tube outlet (D) i ), internal phase solution flow rate (u i ) and the viscosity of the receiving liquid (μ) o Under various operating conditions, the forming mechanism and control law of the structural characteristics of micro-spiral flow, such as pitch (P), diameter (D), amplitude (A), and frequency (Ω), were systematically studied. The evolution and uniformity of the pitch and diameter of micro-spiral flow in the axial direction were analyzed in detail to provide guidance for the preparation of micro-spiral functional materials with diverse structures.

[0084] The pitch is the most important factor affecting the performance of microhelical functional materials. As the internal phase solution flow rate (u) increases... i With the increase of ), the microfluidic exhibits excellent helical morphology within a relatively large internal phase solution flow velocity range of 0.065~0.131 m / s, such as Figure 4 As shown in Figure a. The inner diameter of the injection tube outlet (D) i In parallel experiments with flow rates of 120, 160, and 200 μm, the pitch (P) of the microspiral flow showed a significant linear decreasing trend with increasing internal phase solution velocity. Figure 4 As shown in Figure b. With the change in the inner diameter of the injection tube outlet (D)... i With the increase of amplitude, microfluidics exhibit excellent helical morphology at extremely large scales (specifically, amplitude parameters), such as... Figure 4 As shown in Figure c; simultaneously, with the increase of the inner diameter of the injection tube outlet, the flow rate of the internal phase solution (u) varies. iThe pitch of the micro-spiral flow prepared under conditions of 0.118, 0.147, and 0.177 m / s exhibits an excellent exponential increasing trend, such as... Figure 4 The figure is shown in d. In particular, this method, for the first time, controllably constructs the pitch over a very large range of 2–7 mm, and the pitch exhibits extremely small errors, indicating that this method has significant potential for constructing multi-scale microhelical functional materials. With the increase in the viscosity of the internal phase solution (μ... i With the increase of ), microfluidics exhibit excellent helical morphology, such as Figure 5 As shown in Figure a; simultaneously, with the increase of the viscosity of the internal phase solution, the internal phase solution flow rate (u) varies. i The pitch of the micro-spiral flow prepared under conditions of 0.099, 0.116, and 0.133 m / s showed a significant linear increasing trend, such as... Figure 5 As shown in Figure b. With the increase in the viscosity of the receiving liquid (μ... o With the increase of ), the microfluidic also exhibited excellent helical morphology, such as Figure 5 As shown in Figure c, the amplitude of the micro-spiral flow, in particular, exhibits a significant decreasing trend; simultaneously, with the increase of the receiving liquid viscosity, the flow rate (u) of the internal phase solution varies. i The pitch of the micro-spiral flow prepared under conditions of 0.105, 0.131, and 0.157 m / s exhibits an excellent power-law decreasing trend, such as... Figure 5 As shown in Figure d, compared to the viscosity of the internal phase solution, the viscosity of the receiving liquid has a more significant impact on the pitch of the micro-spiral flow, exhibiting obvious nonlinear characteristics, and achieving controllable adjustment within a wide range of 1~4 mm.

[0085] Furthermore, to evaluate the evolution and stability characteristics of the pitch of the micro-spiral flow under unconfined conditions, a systematic analysis was conducted on the spatial distribution of the pitch along the gravity direction and its variation over time. Multiple continuously formed pitch units can be clearly distinguished in each working condition image, with the pitch gradually decreasing along the z-direction. This phenomenon mainly stems from the continuous viscous damping effect of the receiving liquid on the jet, such as... Figure 6 As shown in Figure a. Furthermore, to evaluate the stability of the microhelical flow over time, a statistical analysis was performed on the first fully formed pitch. The results show that the average value of the first pitch is 2.491 μm, with a CV value of only 4%, exhibiting extremely high temporal stability, such as... Figure 6 As shown in Figure b.

[0086] In the diameter control of micro-spiral flow, different injection tube outlet inner diameters (D) i At flow rates of 120, 160, and 200 μm, the diameter (D) of the microspiral flow varies relatively little with the internal phase solution velocity, remaining approximately constant over a wide velocity range. Figure 7 As shown in Figure a. Further, Figure 7Figure b quantitatively reveals the control relationship and influence law of the injection tube outlet inner diameter on the micro-spiral flow diameter. The micro-spiral flow diameter exhibits a significant exponential increase with the increase of the injection tube outlet inner diameter, and the flow velocities (u) of different internal phase solutions also show this effect. i The curves showing variation under conditions of 0.118, 0.147, and 0.177 m / s are highly consistent. This indicates that in unconfined microfluidics, the inner diameter of the injection tube outlet is the dominant parameter determining the lateral expansion scale of the microhelical flow. Keeping other conditions constant, the diameter of the microhelical flow varies with the viscosity of the internal phase solution (μm). i The variation range is relatively small; as the viscosity of the internal phase solution increases, it only shows a slight decreasing or approximately constant trend, such as... Figure 7 Figure c shows this. This indicates that the viscosity of the internal phase solution has a relatively weak effect on the diameter of the micro-spiral flow; its main role is still in regulating the jet's tortuosity and pitch characteristics, rather than significantly altering the jet's transverse scale. In contrast, the viscosity of the receiving liquid (μ) o The effect of the receiving liquid viscosity on the diameter of the microspiral flow is slightly significant, but the overall change remains limited. With increasing receiving liquid viscosity, the flow rate (u) of the internal phase solution varies. i The diameter of the micro-spiral flow prepared under conditions of 0.105, 0.131, and 0.157 m / s showed a slight increasing trend, such as... Figure 7 As shown in Figure d, this phenomenon may be due to the increased viscosity of the receiving liquid, which causes stronger viscous damping to affect the lateral motion of the jet, slightly reducing its lateral fluctuation amplitude. This results in the micro-spiral flow exhibiting a more compact coiled trajectory in space, manifested as a slight increase in the effective diameter.

[0087] The amplitude (A) of the microhelical flow reflects the oscillation amplitude of the jet in the transverse direction and is an important parameter characterizing the strength of the fluid rope-winding effect. By systematically adjusting the operating conditions, the formation mechanism of the microhelical structure in the unconfined microfluidic system was further revealed. Firstly, under different injection tube outlet inner diameters (D... i Under conditions of 120, 160, and 200 μm, the amplitude of the micro-spiral flow varies relatively little with the internal phase solution velocity, showing a slight linear decreasing trend as the internal phase solution velocity increases. Figure 8 As shown in Figure a, with the increase of the internal phase solution flow velocity, the axial momentum of the jet increases, which somewhat suppresses the relative degree of deflection and oscillation in the lateral direction, resulting in a slight decrease in amplitude. At different internal phase solution flow velocities (u... i The amplitude of the micro-spiral flow prepared under conditions of 0.118, 0.147, and 0.177 m / s showed a significant exponential increase with the increase of the inner diameter of the injection tube outlet, and the variation curves under different internal phase solution flow rates were highly consistent, such as... Figure 8As shown in Figure b, the inner diameter of the injection tube outlet has a dominant effect on the amplitude, similar to the micro-spiral flow in a confined domain. From a physical perspective, a larger injection tube outlet inner diameter produces a coarser jet, giving it a larger inertial scale and lateral oscillation space. With increasing viscosity of the inner phase solution, the amplitude varies at different inner phase solution velocities (u... i The amplitudes of the micro-spiral flows prepared under conditions of 0.099, 0.116, and 0.133 m / s all showed a slow, linear increasing trend, such as... Figure 8 As shown in Figure c, increasing the viscosity of the inner phase solution helps enhance the morphological stability of the jet during the lateral swirling process, allowing it to maintain a continuous and regular helical structure on a larger lateral scale. Unlike the suppression effect of the inner phase solution viscosity on the swirling frequency in pitch control, the inner phase solution viscosity here is more about enhancing the integrity of the jet morphology, thus enabling the lateral oscillation to exist stably on a larger scale without being disrupted by the high shear of the receiving liquid. In contrast, the viscosity of the receiving liquid has a more significant impact on the amplitude of the micro-helical flow, and exhibits a clear power-law decreasing trend, such as... Figure 8 The figure is shown in d. As the viscosity of the external phase fluid increases, the internal phase solution flow rate (u) varies. i The amplitude of the micro-spiral flow prepared under the conditions of 0.105, 0.131, and 0.157 m / s decreased rapidly and tended to stabilize in the higher viscosity range.

[0088] The frequency of the micro-spiral flow reflects the periodic characteristics of the jet's lateral oscillation and is a core indicator characterizing the dynamic evolution rate of the fluid rope effect. At different injection tube outlet inner diameters (D... i Under conditions of 120, 160, and 200 μm, the frequency (Ω) of the microspiral flow showed a significant linear increasing trend with the increase of the internal phase solution velocity, such as... Figure 9 As shown in Figure a. The results from the parallel groups show that the smaller the inner diameter of the injection tube outlet, the steeper the slope of the frequency increase. Specifically, this phenomenon stems from the fact that the increased flow velocity of the inner phase solution enhances the axial inertial force of the jet, accelerating the development rate of the jet bending disturbance, thereby directly increasing the oscillation frequency. The frequency exhibits a significant exponential decreasing trend with increasing injection tube outlet inner diameter, and the frequency varies with different inner phase solution flow velocities (u...). i The curves showing changes at speeds of 0.118, 0.147, and 0.177 m / s highly overlap, as shown below. Figure 9 As shown in Figure b, the inner diameter of the injection tube outlet is the core parameter determining the frequency. From a physical perspective, a larger injection tube outlet inner diameter produces a coarser jet with a thicker viscous boundary layer. This increases the wavelength of the jet's bending disturbance, prolongs the oscillation period, and ultimately leads to a decrease in frequency. This variation occurs at different internal phase solution flow velocities (u...). iUnder conditions of 0.099, 0.116, and 0.133 m / s, the frequency decreases with increasing viscosity of the internal phase solution, exhibiting a power-law decreasing trend. This reflects the inhibitory effect of the internal phase solution viscosity on the development of jet disturbance. Figure 9 As shown in Figure c. At different internal phase solution flow rates (u... i Under conditions of 0.105, 0.131, and 0.157 m / s, the frequency showed a clear linear increasing trend with the increase of the viscosity of the receiving liquid, such as... Figure 9 As shown in Figure d, the increased viscosity of the receiving liquid enhances the interfacial shearing between the jet and the receiving liquid, exacerbating the jet's instability fluctuations and oscillation frequency. When the shearing of the receiving liquid is strong, the jet's perturbation evolution rate reaches saturation, causing the frequency to enter a stable range.

[0089] The temporal stability of the microhelical flow frequency is a core indicator of the controllability of unconfined microfluidic systems, directly reflecting the dynamic consistency and repeatability of the jet flow stabilization process. Under the condition of fixed internal phase solution flow rate and two-phase solution viscosity, the dynamic evolution process of the microhelical flow frequency was investigated. The results show that when the inner diameter of the injection tube outlet (D...)... i When the micro-spiral flow diameter is 100 μm, the average frequency is 8.9 Hz, the CV value is 9%, and the fluctuation range is 6~12 Hz. Figure 10 As shown in Figure a; while when the inner diameter of the injection tube outlet (D) i When the micro-spiral flow diameter is 120 μm, the average frequency of the micro-spiral flow is 9.4 Hz, the CV value is only 4%, and the fluctuation range is 8~11 Hz, exhibiting excellent stability. Figure 10 As shown in Figure b, this difference stems from the influence of the injection tube outlet inner diameter on the initial momentum flux and viscous boundary layer of the jet. A larger injection tube outlet inner diameter produces a coarser jet, whose higher initial momentum flux and thicker viscous boundary layer enhance the jet's ability to resist disturbances, thereby effectively buffering local fluctuations in interface shear and making the frequency-time evolution more stable.

[0090] Based on the unconfined microfluidic system, a correlation formula (as shown in equations (1) to (4)) was established between the structural characteristics of micro-spiral flow, such as pitch, diameter, amplitude, and frequency, and operating conditions, using dimensionless analysis. This was used to reveal the quantitative control law of fluid dynamic parameters on micro-spiral formation. The model selected the Reynolds number (Re) and capillary number (Ca) of the inner phase solution, as well as the viscosity ratio (μ) of the two phase solutions. i / μ o As core variables, Ca and Re are determined solely by the parameters of the internal phase solution itself, while μ... i / μ o This demonstrates the regulating effect of the receiving liquid viscosity. Specifically, for ease of measurement, surface tension (γ) is introduced into the dimensionless number, and in this all-aqueous system, the surface tension is set to 10.-3 N / m.

[0091] In the pitch formula, Re and μ i / μ o The positive exponent indicates that both the increase in the inertial force of the internal solution and the increase in the viscosity of the internal solution can promote the increase in pitch, while the decrease in pitch with the increase of Ca reflects the inhibitory effect of the viscous force of the internal solution on the transverse oscillation of the jet (i.e., the increase in the viscosity of the internal solution). Figure 11 (See Figure a and Equation 1). The former reflects the enhanced jet morphology stability due to the increased viscosity of the internal solution, while the latter stems from the driving force of inertial forces on the development of disturbances. The experimental and predicted values ​​show a high linear correlation, with data points concentrated within the ±20% error band, verifying the predictive ability of this correlation for the pitch of micro-spiral flow and further confirming the synergistic regulation mechanism of inertial-viscosity balance and interfacial interaction in unconfined systems.

[0092] P / D i = 0.17Re 0.43 Ca -0.57 (μ i / μ o ) 1.27 (1)

[0093] In the formula, P / D i The ratio of the micro-spiral flow pitch to the inner diameter of the injection tube outlet, Re is the Reynolds number of the inner phase solution, Ca is the number of capillaries in the inner phase solution, and μ is the number of capillaries in the inner phase solution. i / μ o This is the viscosity ratio of the internal phase solution to the receiving liquid.

[0094] In the diameter formula, the exponents of Re and Ca are both close to 0, indicating that their direct control over the diameter is weak. Therefore, the diameter is mainly determined by the inner diameter of the injection tube outlet, consistent with the Barus effect. Furthermore, the weak positive exponent of the viscosity ratio of the inner phase solution to the receiving liquid also reflects the slight inhibitory effect of the receiving liquid viscosity on the radial expansion of the jet (see...). Figure 11 (See Figure b and Equation 2). The results show that the error between the experimental and predicted values ​​is within ±15%, indicating that the correlation can effectively describe the evolution of the diameter and also reveal the strong dependence of the diameter on the initial jet size in the unconfined system.

[0095] D / D i = 1.88Re -0.0082 Ca 0.0069 (μ i / μ o ) 0.11 (2)

[0096] In the formula, D / D i The ratio of the microspiral flow diameter to the injection tube outlet inner diameter, Re is the Reynolds number of the inner phase solution, Ca is the number of capillaries in the inner phase solution, and μ is the number of capillaries in the inner phase solution.i / μ o This is the viscosity ratio of the internal phase solution to the receiving liquid.

[0097] In the amplitude formula, the positive exponent of Re and the negative exponent of Ca reflect the promoting effect of inertial force on disturbance and the suppressing effect of viscous force of internal phase solution on lateral oscillation. The positive exponent of the viscosity ratio of internal phase solution to receiving liquid further indicates that increasing the viscosity of internal phase solution can enhance the stability of jet morphology, thereby supporting the formation of larger amplitudes (see...). Figure 11 (See Figure c and Equation 3). The results show that the error between the experimental and predicted values ​​is controlled within ±15%, which verifies the reliability of the correlation and further clarifies the dynamic essence of the amplitude being synergistically regulated by the internal phase inertia-viscosity balance and the interfacial viscosity.

[0098] A / D i = 2.19Re 0.091 Ca -0.14 (μ i / μ o ) 0.46 (3)

[0099] In the formula, A / D i The ratio of the micro-spiral flow amplitude to the inner diameter of the injection tube outlet, Re is the Reynolds number of the inner phase solution, Ca is the number of capillaries in the inner phase solution, and μ i / μ o This is the viscosity ratio of the internal phase solution to the receiving liquid.

[0100] In the frequency formula, the negative exponent of Re and the positive exponent of Ca reveal the suppressive effect of inertial force on frequency and the boosting effect of viscous force of the internal phase solution on perturbation frequency. The negative exponent of the viscosity ratio of the internal phase solution to the receiving liquid reflects that the increase in the viscosity of the receiving liquid will further accelerate the perturbation frequency through interfacial shear (see...). Figure 11 (See d-plot and Equation 4). The results show that the error between the experimental and predicted values ​​is within ±25%, indicating that the correlation can effectively predict the frequency variation trend. It also clarifies the dynamic mechanism by which the frequency in the unconfined system is jointly determined by the internal phase viscosity-inertia competition and the interface shear.

[0101] Ω / (u i / D i ) = 0.056Re -0.15 Ca 0.31 (μ i / μ o ) -0.53 (4)

[0102] In the formula, Ω / D i The ratio of the microspiral flow frequency to the inner diameter of the injection tube outlet, Re, the Reynolds number of the inner phase solution, Ca, and μ are all given. i / μo This is the viscosity ratio of the internal phase solution to the receiving liquid.

[0103] Example 2

[0104] In this embodiment, a method for preparing microhelices with controllable structures based on unconfined microfluidics is provided, and the steps are as follows:

[0105] (1) Preparation of two-phase solution

[0106] PEGDA, Irgacure 2959, and F127 were dissolved in deionized water to obtain a prepolymer solution, and then NaAlg was dissolved in the prepolymer solution to obtain an inner phase solution. In the inner phase solution, the mass fraction of PEGDA was 10%~20%, the mass fraction of Irgacure 2959 was 1%~2%, the mass fraction of F127 was 1%, and the mass fraction of NaAlg was 0.1%~2.5%.

[0107] The receiving solution was prepared by dissolving CMC in deionized water; the mass fraction of CMC in the receiving solution was 0%~0.5%.

[0108] (2) Preparation of microhelices

[0109] A micro-spiral flow is constructed using a single nozzle device with the structure described above as a microfluidic device.

[0110] Arrange the single nozzle device vertically so that the outlet end of the injection tube is below the inlet end. Place a collection container containing the receiving liquid below the receiving tube, so that the outlet end of the injection tube is a fixed distance (1 cm) below the liquid surface of the receiving liquid. The collection container is made of quartz glass.

[0111] The inner phase solution is injected into the injection tube using a constant flow syringe pump. The inner phase solution expands and is extruded from the conical opening of the injection tube into the receiving liquid. Under the influence of the fluid rope effect, the inner phase solution becomes unstable due to buckling instability, and orderly coils in the receiving liquid to form a continuous and stable microspiral flow. Applying ultraviolet light to a position within the collection container where the microspiral flow has reached a stable state triggers the photopolymerization reaction of the photopolymerizable polymer monomers in the microspiral flow, resulting in the in-situ preparation of continuous and stable microspirals.

[0112] In this embodiment, microspirals with different structural features were prepared by adjusting the operating conditions such as the viscosity of the internal phase solution, the flow rate of the internal phase solution, the inner diameter of the injection tube outlet, and the viscosity of the receiving liquid.

[0113] To investigate the uniformity of the prepared microspirals, microspirals with different structural characteristics were prepared in batches under different internal phase solution flow rates. The uniformity of the microspirals was characterized by the deviation coefficient (CV) (Equation 5). To investigate the microstructure of the microspirals, the microspirals were dehydrated using a freeze dryer, and the microstructure of the microspirals was observed using a scanning electron microscope. At the same time, the cross-sectional morphology of the microspirals was observed by cutting them.

[0114] (5)

[0115] In Equation 5, X n X is the nth structural eigenvalue. avg is the average of all structural feature values, and N is the number of samples.

[0116] To investigate the recombination ability of the microhelices, Fe3O4 nanoparticles were introduced into the inner phase solution. Magnetic microhelices were prepared using the inner phase solution containing Fe3O4 nanoparticles, and the cut microhelices were placed in deionized water for driving experiments. The preparation method of the inner phase solution containing Fe3O4 nanoparticles was as follows: PEGDA, Irgacure 2959, F127, and Rhodamine B were dissolved in deionized water to obtain a prepolymer solution. NaAlg was dissolved in the prepolymer solution, and then Fe3O4 nanoparticles were added and fully dispersed to obtain the inner phase solution. In the inner phase solution, the mass fraction of PEGDA was 15%, the mass fraction of Irgacure 2959 was 1%~2%, the mass fraction of F127 was 1%, the mass fraction of Rhodamine B was 0.1%, the mass fraction of NaAlg was 0.1%~2.5%, and the mass fraction of Fe3O4 nanoparticles was 3%.

[0117] In this embodiment, PEGDA / NaAlg microhelices with different structural features were successfully prepared. Specifically, to demonstrate the advantages of the method of this invention in preparing microhelices across scales, microhelices were prepared using an injection tube outlet inner diameter of 100–200 μm. All prepared microhelices exhibited excellent helical morphology, complete morphology, and good dimensional uniformity (e.g., ...). Figure 12 (As shown in Figures a~c). In the preparation... Figure 12 In the microspiral configuration shown, the mass fraction of sodium alginate in the inner phase solution was 2.1%, the mass fraction of PEGDA was 15%, and the mass fraction of CMC in the receiving solution was 0.1%.

[0118] Specifically, when the inner diameter of the injection tube outlet is 100 μm, the pitch of the fabricated microhelix can be stably controlled within the range of 0.314–0.412 mm, with a diameter of approximately 0.17 mm, exhibiting a fine microhelix structure. As the inner diameter of the injection tube outlet increases to 140 μm and 200 μm, the pitch can be further extended to 1.773–2.536 mm and 2.959–3.738 mm, respectively, while the diameter simultaneously increases to 0.35 mm and 0.55 mm, achieving cross-scale structural control from the micrometer to the millimeter scale. Overall, by simply adjusting the inner diameter of the injection tube outlet, precise control of the microhelix structural characteristics is achieved within a pitch range of 0.4–3.7 mm, a diameter range of 0.17–0.55 mm, and an amplitude range of 0.7–2.7 μm. Under typical operating conditions, the size distribution of the prepared PEGDA / NaAlg microspirals was statistically analyzed to evaluate the stability of the microspiral preparation method and the structural uniformity of the prepared microspirals. Figure 13 As shown, the pitch, amplitude, and diameter of the microhelices exhibit typical normal distribution characteristics, concentrated in the ranges of 1.940–2.180 mm, 2.100–2.325 mm, and 0.420–0.460 mm, respectively, with CV values ​​of 8%, 5%, and 3%, indicating that the method described in this invention can produce microhelices with highly uniform dimensions. In particular, the low CV value of the diameter directly reflects the precise control of the injection tube outlet inner diameter on the initial jet size, and the rapid morphological locking effect of online photopolymerization to reduce structural distortion. The above experimental results demonstrate that the method described in this invention, through unrestricted microfluidics combined with an online photopolymerization strategy, can not only achieve cross-scale control of microhelices but also ensure their high dimensional uniformity.

[0119] Size uniformity is a core performance indicator for microspiral applications. Furthermore, the uniformity distribution of the microspiral pitch was quantified using CV values ​​under different injection tube outlet inner diameters and internal phase solution flow rates. For example... Figure 14 As shown, for three injection tube outlet inner diameters of 100 μm, 140 μm, and 200 μm, the pitch (P) of the microspiral increases with the internal phase flow rate (Q). i The CV value decreases with increasing diameter, remaining consistently at a low level of 3%–9%. Furthermore, the fluctuation range of the maximum and minimum CV values ​​under various operating conditions is only 2%–4%, indicating that the method described in this invention maintains good dimensional stability under multiple operating conditions. Moreover, as the inner diameter of the injection tube outlet increases from 100 μm to 200 μm, the CV value of the pitch only slightly increases from 7% to 9%, demonstrating that the method maintains good dimensional uniformity in cross-scale fabrication.

[0120] The multi-scale structure of PEGDA / NaAlg microhelices was systematically analyzed using SEM characterization, revealing excellent controllability and structural integrity from macroscopic helical morphology to microscopic surface and cross-sectional morphology. Figure 15 As shown in Figures a~e, on a macroscopic scale, with the adjustment of preparation parameters, the structural features of the microspiral exhibit continuous and uniform changes. The spiral waveform is regular and without obvious breaks or deformation, indicating that the method described in this invention can accurately lock the dynamic coiling morphology of the jet and prepare microspirals with uniform structural height. Figure 15 As shown in the f~g figure, at the microscale, the surface of the microspiral exhibits an interconnected porous structure, which is due to the phase separation effect during solvent evaporation and photocuring. This structure can provide abundant sites for cell adhesion and nutrient delivery. Figure 15 The cross-sectional morphology shown in the h-plot further confirms the compactness and homogeneity of the microhelix interior. No obvious phase separation or defects were found, indicating that PEGDA and NaAlg achieved good molecular blending during the curing process, providing a stable mechanical property basis for the microhelix. This synergistic controllability of the multi-scale structure not only verifies the effectiveness of the method described in this invention in the regulation of microhelix structure, but also reveals the application potential of PEGDA / NaAlg microhelices in biomedicine and tissue engineering.

[0121] By employing an unconfined microfluidic approach combined with online photopolymerization, the continuous large-scale preparation of PEGDA / NaAlg microhelices was achieved, demonstrating the feasibility of their functional modification. Figure 16 As shown in Figures a~b, whether it is a pure polymer microspiral without Fe3O4 nanoparticles ( Figure 16 (Figure a), or the magnetic composite microspiral prepared after introducing Fe3O4 nanoparticles ( Figure 16 As shown in Figure b), the method can be stably sprayed and solidified in an unconfined system to form a continuous and regular helical structure. This verifies the compatibility of the method described in this invention in functional modification and also shows that by simply controlling the composition of the internal phase solution, additional functions such as micro-helical magnetic response can be endowed, providing a technical path for the development of magnetically driven microdevices. Figure 16 Figures c-d visually demonstrate the scalable production capability of the method described in this invention. During a continuous spraying process of 1500 s, the preparation conditions remained stable, producing microspirals with a total length of 16 m. Furthermore, the pitch (1.472 mm) and frequency (7.1 Hz) of the microspirals remained highly stable over the long preparation period. Macroscopically, the large number of prepared microspirals exhibited a uniform orange-yellow color and no obvious filament breakage, indicating that the method possesses excellent continuous production stability and can initially meet the requirements of bio-applications for preparation efficiency and product uniformity. Magnetic attraction experiments were conducted on the prepared magnetic composite microspirals, and the results showed that the magnetic composite microspirals exhibited good magnetic control characteristics, such as... Figure 17As shown in Figures a-b, when the magnet gradually approaches the magnetic composite microhelix, the microhelix exhibits significant deformation under the magnetic field gradient, eventually reaching a state of complete attraction at the wall of the box. In summary, this characteristic of scalable fabrication and functionalization compatibility can effectively expand the application scenarios of microhelices.

[0122] Example 3

[0123] In this embodiment, a method for preparing a microspiral scaffold is provided, the steps of which are as follows:

[0124] (1) Preparation of solutions for each phase

[0125] A prepolymer solution was prepared by dissolving PEGDA, Irgacure 2959, and F127 in deionized water, and an internal phase solution was prepared by dissolving NaAlg in the prepolymer solution. In this step, internal phase solutions of different concentrations were prepared. In the internal phase solutions, the mass fraction of PEGDA was 10%~20%, the mass fraction of Irgacure 2959 was 1%~2%, the mass fraction of F127 was 1%, and the mass fraction of NaAlg was 0.1%~2.5%.

[0126] The receiving solution was prepared by dissolving CMC in deionized water. In this embodiment, receiving solutions of different concentrations were prepared, and the mass fraction of CMC in the receiving solution was 0% to 0.5%.

[0127] Acrylamide (AM) monomer, crosslinking agent N,N'-methylenebisacrylamide (BIS), and photoinitiator Irgacure 2959 were dissolved in deionized water to obtain a casting solution. In the casting solution, the mass fraction of AM was 10%~20%, the mass fraction of BIS was 0.1%~0.2%, and the mass fraction of Irgacure 2959 was 0.1%~0.2%.

[0128] (2) Preparation of microhelices

[0129] A micro-spiral flow is constructed using a single nozzle device with the structure described above as a microfluidic device.

[0130] Arrange the single nozzle device vertically so that the outlet end of the injection tube is below the inlet end. Place a collection container containing the receiving liquid below the receiving tube, so that the outlet end of the injection tube is a fixed distance (1 cm) below the liquid surface of the receiving liquid. The collection container is made of quartz glass.

[0131] The internal phase solution is injected into the injection tube using a constant flow syringe pump. The internal phase solution is squeezed out from the conical opening of the injection tube and expands into the receiving liquid. Under the action of the fluid rope effect, the internal phase solution becomes unstable due to buckling instability and forms a continuous and stable micro-spiral flow in the receiving liquid.

[0132] Applying ultraviolet light to a location in the collection container where the microspiral flow morphology has reached a stable state triggers a photopolymerization reaction of the photopolymerizable polymer monomers in the microspiral flow, thereby obtaining a continuous and stable microspiral in situ.

[0133] (3) Fabrication of microspiral scaffolds

[0134] The aforementioned rotating plate is fixed in the receiving liquid of the collection container. The connecting shaft of the rotating plate is connected to a constant-speed motor located outside the collection container. Then, the end of the micro-spiral is clamped in the groove of the rectangular plate of the rotating plate to achieve fixation. Then, the constant-speed motor drives the rectangular plate to rotate slowly around its own axis to achieve orderly winding and arrangement of the micro-spiral on the rectangular plate. After that, the rotating plate with completed micro-spiral winding is taken out and placed in a casting mold. Casting liquid is added to the casting mold to completely immerse the micro-spiral. Ultraviolet light is applied to the casting mold for 30 seconds to induce homopolymerization of AM monomers in the casting liquid and copolymerization of AM monomers and crosslinking agent BIS until the casting liquid is transformed into hydrogel. Finally, the hydrogel is demolded and removed. The hydrogel is cut or trimmed to disconnect the connection between the hydrogel and the rotating plate. The rotating plate is removed to obtain the micro-spiral scaffold.

[0135] The mass-produced microspirals exhibit a uniform, fluffy stacked morphology, with continuous and uniformly distributed pore structures between the microspirals, such as... Figure 18 As shown in Figure a, after the microhelices are orderly wound and arranged on the rotating plate, the regular spiral waveform and consistent spacing allow for the precise assembly of the tissue scaffold, such as... Figure 18 As shown in Figure b. Figure 18 Figures c to d are optical images of microspiral scaffolds prepared using microspirals of different sizes. The microspiral scaffolds not only retain the fine structure of the microspirals, but also, through the encapsulation and support of the polymer matrix, endow the scaffolds with excellent mechanical stability and structural integrity.

[0136] To investigate the deformation behavior of the microhelices in the microhelical scaffold, tensile tests were conducted on the fabricated microhelical scaffold using a universal tensile testing machine, and the deformation process was recorded using a high-speed microscope. The following are the fabrication process parameters of the microhelical scaffold used to characterize and investigate the deformation behavior of the microhelices. In the inner phase solution, the mass fractions of PEGDA, Irgacure 2959, F127, and NaAlg were 15%, 1%, and 0.1%, respectively. In the receiving solution, the mass fraction of CMC was 0.1%. In the casting solution, the mass fractions of AM, BIS, and Irgacure 2959 were 15%, 0.13%, and 0.17%, respectively. During the fabrication process, the outlet inner diameter of the injection tube was 160 μm, the concentration of the outer phase solution was 0.1%, and the flow rate of the inner phase solution was 80 μL / min.

[0137] The microhelical scaffold was stretched along its length, and the detailed deformation evolution could be observed from the optical images of the stretching process: (1) In the initial stage, the PAM matrix was stretched uniformly, the microhelix maintained its complete helical shape, its pitch gradually increased, and the rest of the structure remained basically unchanged. Figure 19 (a1~a3); (2) In the intermediate stage, the PAM matrix exceeds the fracture limit and reaches the fracture point, and the load begins to transfer to the micro-helices ( Figure 19 (a4 figure); (3) In the later stage, the micro-spiral gradually unfolds and enters the linear stretching stage. As the micro-spiral is stretched, it gradually unfolds completely and bears the main load until it reaches the maximum stress point. At this time, local fracture begins to occur. Figure 19 (a5~a6 figures); (4) In the failure stage, the micro-helix breaks completely, leading to the complete failure of the micro-helix scaffold. Furthermore, Figure 19 Figure b shows the stress-strain curve, which quantifies the deformation process: in the strain range of 0–0.4, the stress rises rapidly with strain, corresponding to the elastic deformation of the PAM matrix; after point a, the stress slightly decreases, reflecting the cracking of the PAM matrix but the effective transfer of load to the microhelix; the stress rises again in the range of b–c, reflecting the load-bearing effect after the microhelix unfolds; after point c, the stress gradually decreases until the microhelix support completely breaks at point d. This mechanical behavior, which combines strength and toughness, stems from the synergistic effect of multi-scale mechanisms. Macroscopically, the three-dimensional structure of the microhelix enhances its mechanical interlocking with the PAM matrix, delaying interfacial debonding; microscopically, the diffusion and secondary polymerization of AM monomers on the surface of the microhelix form a microscale chain entanglement transition zone, improving the interfacial bonding strength; physically, the strongly hydrophilic hydration layer shared by PAM and the microhelix, and the clamping effect generated by polymerization shrinkage, further strengthen the interface. These multi-scale adhesion mechanisms ensure the effective transfer of load from the flexible PAM matrix to the microhelical rigid reinforcing phase, effectively restricting crack initiation and propagation. This is the foundation for structural reinforcement, ultimately enabling the microhelical scaffold to exhibit overall toughness upon fracture. These results not only elucidate the mechanical reinforcement mechanism of the microhelical scaffold but also verify its application potential in soft tissue repair and other scenarios, providing important evidence for designing composite scaffolds that combine high mechanical performance with biocompatibility.

[0138] Furthermore, the effects of tensile direction, number of microhelices, and microhelical amplitude on the mechanical properties of the microhelical scaffold were systematically investigated. Figure 20As shown in Figure a, the stress-strain curves reveal significant differences in the mechanical response of the support under tension along different directions: the peak stress and fracture strain are highest under axial (Axis, along the length of the micro-helices), followed by radial and diagonal tension, with the blank control group showing the lowest. This anisotropy stems from the directional arrangement of the micro-helices: under axial tension, the helical structure of the micro-helices can fully unfold and bear the load, while under radial and diagonal tension, the angle between the micro-helices and the load direction weakens the load transfer efficiency. Figure 20 Figure b confirms this point, showing that the Young's modulus under axial tension is about 33% higher than that of the control group, indicating that the directional arrangement of micro-helices can significantly improve the axial mechanical properties of the stent. Figure 20 Figure c shows that as the number of microhelices (Count) in the scaffold increases from 0 to 45, the Young's modulus of the scaffold exhibits an approximately linear increasing trend, rising from 15 kPa to over 25 kPa. This reflects the cumulative effect of the microhelical reinforcement: more microhelices provide more load transfer paths, further strengthening the interfacial interlocking and chain entanglement effects, thereby improving the overall stiffness of the scaffold. Figure d in Figure 21 shows that as the amplitude of the microhelices increases from the micrometer level (778 μm) to the millimeter level (1.361 mm), the Young's modulus of the scaffold increases from 15 kPa to 23 kPa. This is because larger microhelices have higher moments of inertia and stronger mechanical interlocking effects, which can more effectively restrict the propagation of cracks in the PAM matrix. The above experimental results indicate that by controlling the number and amplitude of microhelices in the microhelical scaffold, the mechanical properties of the scaffold can be precisely controlled within the range of 15–25 kPa, allowing it to match the mechanical requirements of different soft tissues. This multi-factor regulation capability, combined with the aforementioned multi-scale enhancement mechanism, provides key experimental evidence for designing composite microspiral scaffolds that combine customized mechanical properties with biocompatibility, and has important application value in fields such as cartilage repair and tendon regeneration.

Claims

1. A method for preparing biocompatible microscrews with controllable structure based on non-confined microfluidics, characterized in that, Includes the following steps: (1) Preparation of two-phase solution A prepolymer solution is obtained by dissolving a water-soluble photopolymerizable polymer monomer, a photoinitiator, and a surfactant in deionized water. An internal phase solution is obtained by dissolving a water-soluble polymer compound in the prepolymer solution. The viscosity of the internal phase solution is 500~1000 mPa·s. Deionized water was used as the receiving liquid. Alternatively, a water-soluble polymer compound can be dissolved in deionized water to obtain a receiving solution; the viscosity of the receiving solution is 10~20 mPa·s; (2) Preparation of microhelices A microfluidic device is used to construct a micro-spiral flow. The microfluidic device includes an injection tube with a conical outlet. The microfluidic device is arranged vertically so that the outlet end of the injection tube is below the inlet end. A collection container filled with receiving liquid is placed below the receiving tube so that the outlet end of the injection tube is below the liquid surface of the receiving liquid. The internal phase solution is injected into the injection tube using a syringe pump. The internal phase solution is squeezed out from the conical opening of the injection tube and expands into the receiving liquid. Under the action of the fluid rope effect, the internal phase solution becomes unstable due to buckling instability and coils in an orderly manner in the receiving liquid to form a continuous and stable micro-spiral flow. By applying ultraviolet light to a position in the collection container where the micro-spiral flow morphology has reached a stable state, photopolymerization of the photopolymerizable polymer monomers in the micro-spiral flow is initiated, thus preparing micro-spirals.

2. The method of claim 1, wherein the method of fabricating a biocompatible microcoil with controlled structure based on non-confined microfluidics, further comprises: In step (2), the inner diameter of the outlet of the injection tube of the microfluidic device is controlled to be 60~200 μm.

3. The method of claim 1, wherein the method of fabricating a biocompatible microcoil with controlled structure based on non-confined microfluidics, further comprises: In step (2), the flow rate of the internal phase solution is controlled to be 0.01 ~ 0.50 m / s.

4. The method for preparing structurally controllable biocompatible microhelices based on unrestricted microfluidics according to any one of claims 1 to 3, characterized in that, The water-soluble photopolymerizable polymer monomers include polyethylene glycol diacrylate, polyethylene glycol monoacrylate, hyaluronic acid methacrylate, or alginate methacrylate; the water-soluble polymer compounds include sodium alginate, xanthan gum, methylcellulose, or polyethylene glycol.

5. The method for preparing structurally controllable biocompatible microhelices based on unrestricted microfluidics according to any one of claims 1 to 3, characterized in that, In the inner phase solution, the mass fraction of water-soluble photopolymerizable polymer monomers is 10%~20%, the mass fraction of photoinitiator is 1%~2%, the mass fraction of surfactant is 1%~2%, and the mass fraction of water-soluble polymer compound is 0.1%~2.5%.

6. The method for preparing structurally controllable biocompatible microhelices based on unrestricted microfluidics according to any one of claims 1 to 3, characterized in that, The inner phase solution also contains functional materials, and the mass fraction of the functional materials in the inner phase solution is 1% to 10%.

7. A method for preparing biocompatible microspiral scaffolds, characterized in that, Includes the following steps: (1) Preparation of casting liquid The casting solution is obtained by dissolving polymer monomers, chemical crosslinking agents and photoinitiators in water; (2) Preparation of microhelices Microhelices were prepared using the method described in any one of claims 1 to 6; (3) Fabrication of microspiral scaffolds Place the rotating plate in the receiving liquid of the collection container, and fix the end of the microspiral in the groove of the rectangular plate of the rotating plate. Control the rectangular plate of the rotating plate to rotate around its own axis, and wind the microspiral in an orderly manner around the rectangular plate. Take out the rotating plate after the microspiral is wound, place it in the casting mold, add casting liquid to the casting mold to completely immerse the microspiral, apply ultraviolet light to irradiate until the casting liquid turns into hydrogel, cut or cut the hydrogel to break the connection between the hydrogel and the rotating plate, remove the rotating plate, and obtain the microspiral support. The rotating plate is a rectangular plate with grooves on its surface for fixing micro-spirals. A connecting shaft is provided on the rectangular plate, and the rectangular plate is driven to rotate around its own axis by a rotating mechanism.

8. The method for preparing a biocompatible microspiral scaffold according to claim 7, characterized in that, The polymer monomer is a water-soluble photopolymerizable polymer monomer.

9. The method for preparing a biocompatible microspiral scaffold according to claim 7 or 8, characterized in that, In the casting liquid, the mass fraction of polymer monomer is 10%~20%, the mass fraction of chemical crosslinking agent is 0.1%~0.2%, and the mass fraction of photoinitiator is 0.1%~0.2%.

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