Magnetism-temperature dual-response micro-curl body based on micro-channel shrinkage molding and preparation method and application of magnetism-temperature dual-response micro-curl body

Abstract

The invention discloses a magnetic-temperature dual-response micro-curl body based on micro-channel shrinkage molding and a preparation method and application thereof, and belongs to the technical field of micro-nano manufacturing and intelligent materials. According to the method, a two-dimensional compression force field is generated by shrinking a micro-channel, a two-dimensional thin film is induced to be curled into a three-dimensional microstructure, and controllable preparation of the micro-curled body is achieved. The obtained micro-curl body integrates magnetic response and temperature-sensitive characteristics, can realize targeted drug delivery through magnetic field navigation and photo-thermal triggering, and has a wide application prospect in the field of biomedicine. The method is simple in process, low in cost and suitable for batch production, and a new thought is provided for intelligent microcarrier development.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano manufacturing and smart materials technology, specifically a magnetic-temperature dual-response micro-roll body based on microchannel shrinkage molding, its preparation method and application. Background Technology

[0002] Micrometer-scale three-dimensional structures have shown great application potential in fields such as biomedical engineering (e.g., targeted drug delivery, minimally invasive surgery), micro / nano sensing, and microelectromechanical systems (MEMS). Currently, the development of this field faces two major technical bottlenecks: firstly, the efficient and controllable preparation of three-dimensional microstructures is difficult; and secondly, the ability to integrate multiple functions such as actuation, sensing, and release is insufficient.

[0003] Existing fabrication technologies, such as photolithography and electron beam etching, are complex, costly, and difficult to mass-produce complex three-dimensional morphologies. Another mainstream technology is the self-rolling method based on a "sacrificial layer," which involves depositing a thin film with a stress gradient on a substrate, then etching away the underlying sacrificial layer to release stress and allow the film to roll up into a three-dimensional structure. However, this method requires extremely high process control, making it difficult to guarantee yield and consistency, and typically hindering high-throughput production. Furthermore, the structures obtained through this method often have limited functionality, making it difficult to meet intelligent requirements such as integrated "motion-release" systems.

[0004] Therefore, there is an urgent need in this field for a new method that can simply, quickly, and in batches prepare three-dimensional microstructures with multiple functions. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the present invention aims to design and provide a technical solution for a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding, its preparation method, and its applications. By innovatively utilizing the shrinkage microchannel to generate a two-dimensional compressive force field, it is possible to controllably prepare a three-dimensional micro-rolled body with magnetic response and thermosensitive properties, providing advantages for its application in magnetically controlled transport and thermosensitive stimulus-responsive release systems.

[0006] The magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized by: The micro-curled body has a hollow micron-scale cylindrical structure; The micro-curled body contains magnetic nanoparticles, which exhibit magnetic responsiveness. The micro-crescendo contains polycaprolactone and is temperature-responsive.

[0007] The magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized in that: the length of the micron-scale cylindrical structure is 1-10mm, the diameter of the cylindrical surface is 300-500μm, and the wall thickness of the cylindrical surface is 5-20μm.

[0008] The magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized by: being able to generate directional movement under the action of an external magnetic field; and being able to unfold and deform its structure when the ambient temperature rises to 60°C to 90°C.

[0009] The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized by the following steps: 1) Dissolve styrene-butadiene-styrene block copolymer (SBS):polycaprolactone (PCL) in an organic solvent at a mass ratio of 40-90:10-60 to prepare a homogeneous solution with a concentration of 0.05-0.15 g / ml. Add 5-15 wt% of magnetic nanoparticles of total solute and mix evenly to form a mixture. 2) The obtained mixture is made into a gel film and then dried to obtain a composite film; 3) Cut the composite film into prefabricated films of regular geometric shapes; 4) The preformed film is dispersed in water and flows through a contraction microchannel to form a temporary micro-curled structure; 5) In the microchannel, the temporary micro-coiled structure is heated and then cooled to set; 6) Extrude the microchannels to obtain functional micro-rolled bodies.

[0010] In step 1) of this invention: the ratio of SBS to PCL is the core parameter for controlling the mechanical strength and thermo-responsive characteristics of the composite film and its derived micro-rolls. SBS, as an elastomer framework, provides structural elasticity and strength. A higher SBS ratio results in a more rigid composite film, requiring greater fluid driving force for rolling, but also better mechanical stability of the molded micro-rolls. PCL, as a thermoplastic crystalline polymer, provides heat-setting capability and thermo-responsiveness. A higher PCL ratio allows the material to soften more easily at lower temperatures, which is beneficial for heat setting and results in a faster and more significant thermo-responsiveness, but may sacrifice some structural strength. The concentration of the homogeneous solution directly determines the final film thickness; a higher concentration results in a thicker film, leading to an increase in the wall thickness of the micro-rolls. The film thickness needs to match the channel dimensions; excessive thickness may lead to difficulty or incomplete rolling.

[0011] The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized in that, in step 1), 0-1 wt% of a fluorescent dye, preferably 0.4-0.6 wt%, of the total solute mass is added; the organic solvent is toluene; the mass ratio of styrene-butadiene-styrene block copolymer to polycaprolactone is 50-70:30-50; the concentration of the homogeneous solution is 0.1-0.12 g / ml; the magnetic nanoparticles are iron oxide nanoparticles with an average particle size of 10 nm-50 nm, preferably 20 nm-30 nm, and the amount of magnetic nanoparticles added is 8-12 wt% of the total solute mass. The higher the content of magnetic nanoparticles, the higher the magnetization of the micro-rolled body, and the faster the magnetic torque and movement speed generated under the same magnetic field. However, excessively high content affects the film-forming properties, mechanical properties, and fluorescence effect of the material itself, while particle size affects the dispersion uniformity.

[0012] The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized in that, in step 2): the method for preparing the gel film is spin coating or blade coating; the drying treatment is atmospheric pressure drying or vacuum drying, the drying temperature is 60℃-100℃, and the drying time is 12-48 hours to ensure complete removal of solvent and avoid redissolution or defects in the subsequent aqueous phase process; the thickness of the composite film is 5-20μm.

[0013] The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized in that, in step 3), the regular geometric shape is a square or rectangle with a side length of 1-10 mm, and is prepared by laser cutting or mechanical cutting. The size of the preform must match the diameter of the shrinkage microchannel; if the size is too large, it may cause blockage, and if it is too small, it may result in insufficient curling.

[0014] The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized in that, in step 4), the microchannel is a shrinkage tubular structure with a stable shrinkage section length of 0.5-2 cm and a cross-sectional diameter of 300-500 μm, ensuring that the preform has sufficient time to complete the roll-up. If the length is too short, the roll-up may be insufficient. The preform is injected into the microchannel through an injection pump at a flow rate of 0.1 mL / min-1 mL / min, preferably 0.5 mL / min-0.8 mL / min. If the flow rate is too fast, the shear force will be too large, resulting in irregular roll-up or even tearing of the film. If the flow rate is too slow, the preparation efficiency will be affected.

[0015] The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding is characterized in that, in step 5), the heating and cooling methods are as follows: the heating and cooling are performed in a water bath, with the temperature raised to 60-90℃ and held for 1-5 minutes to ensure sufficient heat conduction, allowing the entire structure to soften uniformly and release internal stress, thus completing the shaping; the cooling temperature range is 10-50℃, held for 1-5 minutes, rapid cooling allows the PCL phase to recrystallize, fixing the rolled shape. The cooling rate and final temperature affect the crystallinity of PCL, which in turn affects its subsequent response temperature threshold and unfolding speed as a temperature-sensitive element.

[0016] The micro-coiled bodies prepared by the method described in this invention are used in magnetically controlled transport systems and thermosensitive stimulus-responsive release systems.

[0017] The core working principle of this invention lies in the ingenious utilization of the synergistic effect of fluid mechanics and the phase transition behavior of smart materials, achieving one-step controllable molding and functional integration from two-dimensional planar preforms to three-dimensional microstructures. Compared with existing technologies, this invention has the following significant advantages: 1. Two-dimensional compression molding: When a two-dimensional preform film dispersed in water flows through a constricting microchannel, it is subjected to a two-dimensional compressive force field generated by the rapid reduction of the channel's cross-section. Under the action of this force field, the edges of the preform are subjected to uniform pressure pointing towards the center, thereby overcoming the rigidity of its planar structure and exhibiting stable and controllable curling behavior, ultimately forming a temporary, hollow cylinder-like three-dimensional structure. This process avoids the dependence on sacrificial layers in traditional methods, resulting in high molding efficiency, simple equipment, and convenient operation.

[0018] 2. Heat Setting: The fixation of temporary curled structures relies on the intelligent response characteristics of the material itself. Polycaprolactone (PCL) in the preform, as a crystalline polymer, has a specific glass transition temperature / melting point. When the temporary curled structure enters the microchannel stabilization section and undergoes heating, the PCL phase softens, and the molecular chain mobility is enhanced, allowing the entire structure to reach an easily adjustable plastic state after stress relaxation. The subsequent rapid cooling process re-solidifies the PCL phase, thus permanently freezing the curled shape and obtaining a structurally stable micro-curled body. By controlling the heating temperature and time, the setting effect can be precisely controlled. By precisely controlling the matching relationship between the preform size and the microchannel parameters, the size and morphology of the micro-curled body can be precisely controlled, resulting in good product consistency.

[0019] 3. Magnetic-thermal dual response function is realized: Magnetic responsiveness: Magnetic nanoparticles (such as Fe3O4) uniformly dispersed in the composite matrix make the micro-curled body a micro-magnet. Under the action of an external magnetic field, the micro-curled body will be subjected to magnetic torque and magnetic force, thereby generating directional rolling or movement, realizing magnetically controlled navigation motion.

[0020] Thermosensitive responsiveness: PCL, as a shaping material, is also a thermosensitive element. When the ambient temperature rises again above its softening temperature, the PCL phase softens again, causing the constraint force maintaining the micro-rolled structure to disappear, and the structure gradually unfolds due to elastic recovery. This controllable deformation capability allows it to act as a switch, realizing the thermosensitive triggering release of the internal encapsulation.

[0021] This invention successfully fabricates an intelligent micro-actuator integrating actuation and release functions through a physicochemical process of hydrodynamic forming-thermosetting and the combination of material functions of magnetic particles and temperature-sensitive polymers. The micro-rolled body simultaneously possesses the magnetic response characteristics of magnetic nanoparticles and the temperature-sensitive characteristics of PCL, achieving a synergistic effect of motion control and deformation release; based on the continuous flow characteristics of shrinkage microchannel technology, high-throughput fabrication of microstructures can be achieved, making it suitable for large-scale production. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of the preparation method of the present invention; Figure 2 Fluorescence micrographs of the initial preform film (left) and micro-curled body (right) of Embodiment 1 of the present invention.

[0023] Figure 3 Fluorescence micrograph of the magnetically controlled motion process of the micro-coil prepared in Example 1 of the present invention in a maze; Figure 4 Fluorescence micrograph of the temperature-responsive release process of the micro-rolled gel microspheres prepared in Example 1 of the present invention. Detailed Implementation

[0024] The embodiments of the technical solution of the present invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0025] 1) Dissolve SBS and PCL in toluene at a mass ratio of 90:10 to prepare a homogeneous solution with a concentration of 0.05 g / ml. Add Fe3O4 nanoparticles (average particle size 20 nm) equivalent to 5 wt% of the total mass of SBS and PCL, add 0.5 wt% fluorescent dye, and stir magnetically for 24 hours to mix evenly. 2) The above mixture was spin-coated onto a clean glass substrate to form a gel film, which was then vacuum-dried at 60°C for 48 hours to obtain a composite film with a uniform thickness of about 5 μm. 3) Using laser cutting technology, the composite film is cut into 1mm × 1mm square preforms; 4) Microchannel shrinkage molding: The preform is dispersed in deionized water and injected into the micro-shrinkage channel using a syringe pump at a flow rate of 0.1 ml / min. The stable section of the shrinkage channel has a length of 0.5 cm and a cross-sectional diameter of 300 μm. As the preform flows through the shrinkage channel, it curls under the stretching action of the two-dimensional flow field, forming a temporary curled body at the stable section. 5) In the stabilization section of the contracted microchannel, the water temperature is rapidly raised to 60℃ using an external water bath circulation system and held for 1 minute to soften and deform the PCL phase. Subsequently, the temperature is rapidly reduced to 10℃ and held for 1 minute for setting.

[0026] 6) Functional micro-coiled bodies are collected from the microchannel outlet.

[0027] Figure 1 The complete preparation process of the present invention is illustrated schematically. Figure 2 The left image shows a fluorescence microscope photograph of the cut square composite film preform (corresponding to the parameters of Example 1), showing its regular shape and clear edges. The right image shows the functional micro-roll body obtained after shrinking microchannel molding and shaping. It can be observed that it successfully transformed from a two-dimensional film into a regular three-dimensional hollow cylindrical structure with complete structure, indicating that the molding process is effective and controllable. Example 2

[0028] 1) Dissolve SBS and PCL in toluene at a mass ratio of 40:60 to prepare a homogeneous solution with a concentration of 0.15 g / ml. Add Fe3O4 nanoparticles (average particle size 30 nm) equivalent to 15 wt% of the total mass of SBS and PCL and 1 wt% of fluorescent dye. Stir magnetically for 24 hours to mix evenly. 2) The above mixture was coated onto a clean glass substrate to form a gel film, which was then dried at 80°C under normal pressure for 24 hours to obtain a composite film with a uniform thickness of about 20 μm. 3) Using laser cutting technology, the composite film is cut into rectangular preforms of 1mm × 10mm; 4) Microchannel shrinkage molding: The preform is dispersed in deionized water and injected into the micro-shrinkage channel using a syringe pump at a flow rate of 1 ml / min. The stable section of the shrinkage channel has a length of 2 cm and a cross-sectional diameter of 500 μm. As the preform flows through the shrinkage channel, it curls under the stretching action of the two-dimensional flow field, forming a temporary curled body at the stable section. 5) In the stabilization section of the contracted microchannel, the water temperature is rapidly raised to 90℃ using an external water bath circulation system and held for 5 minutes to soften and deform the PCL phase. Subsequently, the temperature is rapidly reduced to 50℃ and held for 5 minutes for setting.

[0029] 6) Functional micro-coiled bodies are collected from the microchannel outlet. Example 3

[0030] 1) Dissolve SBS and PCL in toluene at a mass ratio of 60:40 to prepare a homogeneous solution with a concentration of 0.11 g / ml. Add Fe3O4 nanoparticles (average particle size 25 nm) equivalent to 10 wt% of the total mass of SBS and PCL. Do not add fluorescent dye. Stir magnetically for 24 hours to mix evenly. 2) The above mixture was spin-coated onto a clean glass substrate to form a gel film, which was then vacuum-dried at 100°C for 12 hours to obtain a composite film with a uniform thickness of about 12 μm. 3) Using laser cutting technology, the composite film is cut into rectangular preforms of 5mm × 5mm; 4) Microchannel shrinkage molding: The preform is dispersed in deionized water and injected into the microchannel shrinkage channel using a syringe pump at a flow rate of 0.65 ml / min. The stable section of the shrinkage channel has a length of 1.2 cm and a cross-sectional diameter of 400 μm. As the preform flows through the shrinkage channel, it curls under the stretching action of the two-dimensional flow field, forming a temporary curled body at the stable section. 5) In the stabilization section of the contracted microchannel, the water temperature is rapidly raised to 75℃ using an external water bath circulation system and held for 2.5 minutes to soften and deform the PCL phase. Subsequently, the temperature is rapidly reduced to 30℃ and held for 2.5 minutes for setting.

[0031] 6) Functional micro-coiled bodies are collected from the microchannel outlet.

[0032] The following experiments and comparative data further demonstrate the beneficial effects of the present invention.

[0033] Experiment 1: Maze Experiment 1) A flat maze model is made by attaching fluorescent tape to a glass plate; 2) Take the functional micro-coil prepared in Example 1 and place it in the prefabricated planar maze model described above. The width of the maze passage is 1.1 mm. Under an inverted fluorescence microscope, a magnetic field is applied using a magnet. Figure 3 As shown, under the drive of a magnetic field, the micro-curled body can move directionally along a preset path (indicated by the dashed arrow in the figure) in a maze passage, successfully avoiding dead ends, and finally moving from the starting point to the end point. This experiment intuitively demonstrates that the prepared micro-curled body has good magnetic responsiveness and controllable motion capability.

[0034] Experiment 2: Thermosensitive Release Gelatin Microsphere Experiment 1) Prepare gelatin microspheres loaded with green fluorescent pigment (FITC) as model carriers.

[0035] 2) Take the preformed film prepared in Example 1 and pass it together with the fluorescent gelatin microsphere suspension through a constricted microchannel so that the microspheres are wrapped in the hollow cavity of the micro-rolled body.

[0036] 3) Place the micro-rolls loaded with fluorescent microspheres in a pure water observation chamber. Under a fluorescence microscope, heat the micro-rolls to 80°C using a water bath. Figure 4 As shown, under heating stimulation, the microcoil deforms and gradually unfolds, releasing the green fluorescent gelatin microspheres encapsulated within it rapidly in about 30 seconds. Further research indicates that the release rate significantly increases with increasing temperature; the specific unfolding times are shown in Table 1. This process directly demonstrates that the microcoil structure possesses excellent temperature-responsive release capabilities.

[0037] Table 1: Time for complete unfolding of micro-curled bodies at different temperatures Temperature (°C) 60 70 80 90 Time to fully unfold the micro-curled body (s) 80 ±10 45 ±5 30 ± 3 25± 2 The data in Table 1 show that as the temperature increases from 60℃ to 90℃, the complete unfolding time of the micro-rolled body significantly decreases from (80 ± 10) s to (25 ± 2) s, exhibiting a clear positive temperature dependence. This trend is consistent with the thermosensitive response mechanism of the material system, reliably confirming that the unfolding and release behavior of this structure can be effectively controlled by temperature.

[0038] Experiment 3: Statistical test of micro-curled body morphology under different process parameters, see Table 2.

[0039] Table 2: Statistical analysis of micro-curled body morphology under different process parameters (n=50) Example SBS:PCL quality ratio Precast component dimensions (mm) Flow channel diameter (μm) Average diameter (μm) Coefficient of variation (CV) of diameter Average length (mm) Coefficient of variation (CV) of length Average wall thickness (μm) 1 90:10 1×1 300 305 ± 15 4.9% 1.0 ± 0.12 12.0% 5.2 ± 0.3 2 40:60 1×10 500 495 ± 22 4.4% 9.8 ± 0.5 5.1% 20.5 ± 1.8 3 60:40 5×5 400 398 ± 18 4.5% 5.1 ± 0.3 5.9% 12.1 ± 0.4 Note: Data is expressed as “mean ± standard deviation”; coefficient of variation (CV) = (standard deviation / mean) × 100%, the smaller the CV value, the better the homogeneity.

[0040] Table 2 shows that the coefficients of variation (CV) of the key dimensions (diameter, length, and wall thickness) of the micro-rolled bodies prepared by the method of the present invention under different process parameters are all less than 12%, with the CV value of the diameter being less than 5%. This fully demonstrates that the method of the present invention has excellent morphology controllability and intra-batch consistency, and can achieve precise control of the final product size by adjusting the preform size and flow channel parameters.

[0041] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding, characterized in that: The micro-curled body has a hollow micron-scale cylindrical structure; The micro-curled body contains magnetic nanoparticles, which exhibit magnetic responsiveness. The micro-crescendo contains polycaprolactone and is temperature-responsive.

2. The magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 1, characterized in that: The length of the micron-scale cylindrical structure is 1-10 mm, the diameter of the cylindrical surface is 300-500 μm, and the wall thickness of the cylindrical surface is 5-20 μm.

3. The magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 1, characterized in that: It can generate directional movement under the influence of an external magnetic field; when the ambient temperature rises to 60℃ to 90℃, its structure can undergo unfolding deformation.

4. The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 1, characterized in that... Includes the following steps: 1) Dissolve styrene-butadiene-styrene block copolymer: polycaprolactone in an organic solvent at a mass ratio of 40-90:10-60 to prepare a homogeneous solution with a concentration of 0.05-0.15 g / ml. Add 5-15 wt% of magnetic nanoparticles of total solute and mix evenly to form a mixture. 2) The obtained mixture is made into a gel film and then dried to obtain a composite film; 3) Cut the composite film into prefabricated films of regular geometric shapes; 4) The preformed film is dispersed in water and flows through a contraction microchannel to form a temporary micro-curled structure; 5) In the microchannel, the temporary micro-coiled structure is heated and then cooled to set; 6) Extrude the microchannels to obtain functional micro-rolled bodies.

5. The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 4, characterized in that... In step 1), 0-1 wt% of fluorescent dye, preferably 0.4-0.6 wt%, of the total solute mass is added; the organic solvent is toluene; the mass ratio of styrene-butadiene-styrene block copolymer to polycaprolactone is 50-70:30-50; the concentration of the homogeneous solution is 0.1-0.12 g / ml; the magnetic nanoparticles are iron oxide nanoparticles with an average particle size of 10 nm-50 nm, preferably 20 nm-30 nm, and the amount of magnetic nanoparticles added is 8-12 wt% of the total solute mass.

6. The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 4, characterized in that... In step 2): the method for preparing the gel film is spin coating or blade coating; the drying treatment is atmospheric pressure drying or vacuum drying, the drying temperature is 60℃-100℃, and the drying time is 12-48 hours; the thickness of the composite film is 5-20μm.

7. The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 4, characterized in that... In step 3): the regular geometric shape is a square or rectangle with a side length of 1-10mm, and is cut by laser or mechanical cutting.

8. The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 4, characterized in that... In step 4): the microchannel is a constricting tubular structure with a stable constriction section length of 0.5-2cm and a cross-sectional diameter of 300-500μm; the preform is injected into the microchannel by an injection pump at a flow rate of 0.1mL / min-1mL / min, preferably 0.5mL / min-0.8mL / min.

9. The method for preparing a magnetic-thermal dual-response micro-rolled body based on microchannel shrinkage molding as described in claim 4, characterized in that... In step 5): the heating and cooling methods are water baths, heating to a range of 60-90℃ and holding for 1-5 minutes; the cooling temperature range is 10-50℃ and held for 1-5 minutes.

10. The application of a micro-coil prepared by the method of any one of claims 4-9 in a magnetically controlled transport system and a thermosensitive stimulus-responsive release system.

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