Magnetic interface open type fluid chip and preparation method thereof

Abstract

The invention provides a magnetic interface open type fluid chip and a preparation method thereof, and belongs to the technical field of microfluidics and millifluidics. The method comprises the following steps: performing standardization treatment on ferroferric oxide powder to obtain magnetic hydrophobic particles; then wrapping the target liquid with the particles through controllable shaking to form a smooth liquid cake with a magnetic response core-shell structure; dehydrating the smooth liquid cake through programmed stepped heating evaporation treatment to form a wrinkled liquid cake; and finally, cutting and shaping the wrinkled liquid cake by using laser to obtain the magnetic interface open type fluid chip. The magnetic particles form a stable wrapping layer on a liquid-gas interface, so that the chip structure can stably exist in the air without being supported by an oil phase; meanwhile, the optical fiber laser is used for accurately cutting the liquid cake, the channel configuration can be flexibly reconstructed on site according to requirements, and the problems that in the prior art, the environment dependence is high, and the configuration is solidified are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of microfluidics and microfluidics technology, and relates to open fluidic chips, specifically to a magnetic interface open fluidic chip and its fabrication method. Background Technology

[0002] Microfluidics and microfluidics, with their highly efficient and precise control over fluids and reaction processes at the microscale, have demonstrated significant advantages in chemical synthesis, bioanalysis, and materials screening, particularly for handling precious or trace samples. They offer significant value compared to traditional macroscopic reaction systems such as beakers and reaction vessels. This technology improves reaction efficiency, reduces reagent consumption, and enhances process controllability through miniaturization and integrated design. However, the fully enclosed solid-state channel structure commonly used in mainstream micro / microfluidic systems, while providing mechanical stability and airtightness, hinders direct real-time interaction with the external environment. Specifically, it makes it difficult to conveniently introduce or remove samples and reagents as needed, and to implement real-time in-situ detection and intervention. This closed nature severely limits the application of the technology in reaction processes requiring dynamic feedback, real-time adjustment, or multi-point sampling.

[0003] To overcome this limitation, open micro / millifluidic technology based on permeable and interactive channel design has emerged. The resulting open channels allow needles to pierce their interfaces, enabling convenient material handling and in-situ monitoring and intervention, significantly improving operational flexibility. However, existing open systems still have key bottlenecks: most devices need to be completely immersed in a supporting liquid environment (such as an oil phase) to maintain their structure, greatly limiting the ability to operate directly in air; at the same time, the channel configuration is usually solidified in one step during manufacturing, making it impossible to adjust or reshape on-site according to experimental needs; and for open particle wall systems that can maintain their structure or shape reconstruction in air, their fabrication process often relies on manual operation. In addition, in terms of functional integration, existing technologies struggle to achieve external field control of open fluidic chips. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a magnetic interface open fluid chip and its fabrication method, thereby solving the technical problems of existing open fluid chip fabrication technologies, such as reliance on a liquid environment to maintain the structure, fixed and non-reconfigurable pipe shapes, and the need for manual fabrication.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for fabricating a magnetic interface open fluidic chip includes the following steps: Step 1: Standardize the iron oxide powder to obtain magnetic hydrophobic particles: Anneal the iron oxide powder in air at a temperature of 200–400°C (preferably 300°C) for 1–3 hours (preferably 2 hours); after annealing, disperse the powder in anhydrous ethanol and sonicate it at a power of 400–600W (preferably 500W) for 20–30 minutes (preferably 25 minutes); then collect the particles by centrifugation at 8000–12000 rpm (preferably 8000 rpm) for 5–15 minutes (preferably 10 minutes) and redisperse them in toluene; add 3%–5% (by weight of the particles) of n-octadecyltrimethoxysilane to the system and reflux it at 70–90°C (preferably 80°C) under nitrogen protection for 4–6 hours; after the reaction, separate and collect the particles by magnetic field and wash them sequentially with toluene and anhydrous ethanol; after washing, first use 1500–2000... Centrifuge at rpm for 10-15 minutes, then centrifuge at 4000-5000 rpm for 10-15 minutes, and collect the precipitate; dry the precipitate at 50-80℃ (preferably 60℃) for 8-24 hours (preferably 12 hours) to obtain standardized magnetic hydrophobic particles.

[0006] Step 2: The particles are encapsulated in the target liquid to form a smooth liquid cake with a magnetically responsive core-shell structure by controlled shaking: Magnetic hydrophobic particles are spread on a base with a superhydrophobic coating to form a powder bed; the target liquid is dropped into the center of the powder bed; and then the mixture is shaken at a frequency of 150-250 rpm for 30-60 seconds to form a smooth liquid cake with a magnetically responsive core-shell structure.

[0007] Step 3: Dehydrate the smooth liquid cake to form a wrinkled liquid cake through a programmed stepped heating evaporation process (the porous granular shell gives the liquid cake openness, thus allowing for evaporation and dehydration): The core-shell structured smooth liquid cake is rolled and transferred onto a base with a superhydrophobic coating on its surface; then it is maintained at 25°C for 4–6 minutes; subsequently, the temperature is increased in steps of 5°C per stage, and maintained for 3–4 minutes after each increase; it is maintained at the final temperature until the mass loss rate reaches 85%–98%, thus obtaining the wrinkled liquid cake; the final temperature is 37–40°C.

[0008] Step four: Use a laser to cut and shape the wrinkled liquid cake to obtain a magnetic interface open fluid chip: Place the base carrying the wrinkled liquid cake in the processing area of ​​the fiber laser engraving equipment and adjust it to the laser focal plane; input the preset channel pattern into the control system, set the laser power to 10-18 W and the cutting speed to 0.3-1.5 mm / s, and start cutting from the edge of the wrinkled liquid cake; after cutting, an open fluid channel with magnetic response characteristics is obtained, and a magnetic interface open fluid chip is produced.

[0009] The present invention also has the following technical features: Specifically, in step one, the particle size of the iron oxide powder is 1–10 μm.

[0010] Specifically, in step three, the proportion of the wrinkled liquid cake drained is 85wt% to 98wt%.

[0011] Specifically, in steps two and three, the superhydrophobic coating is made of silicon dioxide.

[0012] Specifically, in step four, the laser wavelength used for cutting is 1064 nanometers.

[0013] Specifically and preferably, in step four, when the laser power is greater than 15 W, or the thickness of the wrinkled liquid cake is greater than 1.5 mm, or the cutting speed is less than 0.5 mm / s, the cutting is carried out in a nitrogen atmosphere with a nitrogen pressure of 50-100 kPa.

[0014] The present invention also protects a magnetic interface open fluid chip prepared by the method described above, the chip comprising: a body and open fluid channels engraved on the body.

[0015] Specifically, the main body is a wrinkled liquid cake formed after dehydration of a smooth liquid cake with a magnetically responsive core-shell structure.

[0016] Specifically, the magnetically responsive core-shell structure smooth liquid cake is made of iron oxide and the target liquid.

[0017] Compared with the prior art, the present invention has the following technical effects: (I) This invention enables the chip structure to exist stably in the air without the need for oil phase support by forming a stable coating layer of magnetic particles at the liquid-gas interface; at the same time, the liquid cake is precisely cut by using fiber laser, and the channel configuration can be flexibly reconfigured on site according to the needs, which effectively solves the problems of strong environmental dependence and configuration solidification of the existing technology.

[0018] (II) This invention combines the standardized preparation of magnetically responsive iron oxide particles, programmed step heating evaporation and laser cutting technology to realize the automated and digital rapid prototyping of magnetically responsive open fluid chips.

[0019] (III) The fluid channel prepared by this invention possesses inherent magnetic response characteristics, enabling non-contact, programmable fluid drive and manipulation without the need for external functional components. This method utilizes an external magnetic field to achieve efficient, flexible, and biocompatible control of the fluid within the channel, significantly expanding the application potential of open-source chips in dynamic reactions and automated processes.

[0020] (IV) This invention ensures the consistency and repeatability of chip fabrication through particle standardization pretreatment and precision evaporation process; the overall method has the advantages of simple operation, low cost and controllable process, and is easy to promote and use in fields that require open, reconfigurable and intelligent fluid manipulation, such as biological detection, chemical synthesis and cell culture. Attached Figure Description

[0021] Figure 1 A schematic diagram of the standardized preparation equipment and process for magnetic iron oxide hydrophobic particles.

[0022] Figure 2 This is a schematic diagram of the apparatus and process for preparing a smooth liquid cake with a core-shell structure based on controllable shaking magnetic response.

[0023] Figure 3 A schematic diagram of the apparatus and process for preparing wrinkled liquid cakes based on programmed step heating evaporation.

[0024] Figure 4 A schematic diagram of a liquid cake cutting device based on a fiber laser.

[0025] Figure 5 A real-life photo showing the cutting and fabrication process of a dumbbell-shaped magnetic open-cell microfluidic chip.

[0026] Figure 6 A real-world demonstration image shows a magnetic open-loop microfluidic chip achieving contactless translation and connection under magnetic field control. The image shows a "bar"-shaped magnetic microfluidic channel being attracted by a magnetic element (with a magnetic support steel ruler at its end) to translate non-contactly between two other non-contact magnetic microfluidic chip channels, connecting to both channels and ultimately achieving full connectivity of the entire magnetic microfluidic chip channel system.

[0027] The labels in the diagram represent the following: 1-muffle furnace, 2-ultrasonic disperser, 3-centrifuge, 4-solventothermal reaction apparatus, 5-vacuum drying oven, 6-magnetic hydrophobic particles, 7-smooth liquid cake preparation vessel, 8-circular shaker, 9-core-shell structured smooth liquid cake, 10-base, 11-precision evaporation platform, 12-wrinkled liquid cake, 13-laser engraving equipment, 14-lifting platform; 701-superhydrophobic coating, 901-liquid core, 1101-precision temperature control module, 1102-real-time quality monitoring unit.

[0028] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, all instruments and materials used in this invention are those known in the art.

[0030] The technical concept and principle of this invention are as follows: First, the magnetic powder of iron oxide is standardized and hydrophobically modified and graded by a particle standardization processing device to obtain magnetic hydrophobic particles with good monodispersity (6). Then, in the superhydrophobic smooth liquid cake preparation vessel (7) of the core-shell structure smooth liquid cake generation device, the magnetic particles are wrapped with the target liquid by the controllable shaking of the circumferential shaker (8) to form a magnetic response core-shell structure smooth liquid cake (9) with uniform structure. Subsequently, the smooth liquid cake (9) is transferred to the base (10) of the liquid cake preparation device and is precisely drained by the programmed step heating evaporation process of the precision evaporation platform (11) to transform it into a wrinkled liquid cake (12) with a vertical height much smaller than the horizontal width and in a surface blockage state. Finally, the wrinkled liquid cake (12) is cut and shaped according to the preset pattern by the fiber laser engraving equipment (13) of the laser cutting and shaping device. By optimizing the laser power and cutting speed, and supplementing with particle replenishment, parameter adjustment or secondary dehydration measures when necessary, an open fluid channel with specific morphology and magnetic response functional characteristics is finally obtained.

[0031] Specifically, each step of the present invention and its function are as follows: Step 1: Standardization of Fe3O4 powder to obtain magnetic hydrophobic particles: To achieve stable fabrication of high-performance open-loop fluidic chips, it is necessary to first obtain core powder materials with good monodispersity, strong hydrophobicity, and magnetic response. This step involves a series of standardized pretreatments of commercial Fe3O4 micron powder in a particle standardization device. First, the commercial powder is placed in a muffle furnace (1) and annealed in an air atmosphere for 2 hours. This is intended to effectively remove surface-adsorbed organic impurities and stabilize its crystal structure. After annealing, the powder is dispersed in anhydrous ethanol and ultrasonically treated for 20-30 minutes using an ultrasonic disperser (2) to completely break up the soft agglomerates between particles and form a initially well-dispersed suspension. Subsequently, the suspension is centrifuged at high speed (8000 rpm, 8-15 minutes) using a centrifuge (3) to collect the particle precipitate and redisperse it in toluene solvent. Next, the system was transferred to a solvothermal reaction apparatus (4), and 3%–5% (by mass of the particles) of n-octadecyltrimethoxysilane (OTS) was added as a hydrophobicating agent. The reaction was carried out under nitrogen protection in an oil bath at 80°C with magnetic stirring and reflux for 4–6 hours. This solvent-phase modification process ensured that the long-chain alkylsilane was firmly and uniformly grafted onto the particle surface via covalent bonds, forming a dense monomolecular hydrophobic layer. After the reaction, the modified particles were collected by magnetic field separation and washed repeatedly with toluene and anhydrous ethanol to remove residual reagents. To obtain high-quality powder with a concentrated particle size distribution, a stepped centrifugation method was used for fine classification: the particle suspension finally dispersed in ethanol was first centrifuged at 1500-2000 rpm for 5-15 minutes to remove undispersed large agglomerates. After collecting the supernatant, the speed was further increased to 4000-5000 rpm for 10-15 minutes. The precipitate obtained was the hydrophobic magnetic iron oxide particles (6) with good monodispersity in the target particle size range (1-10 μm). Finally, the obtained product was placed in a vacuum drying oven (5) and dried at 60°C for 12 hours to obtain a standardized magnetic powder (6) with stable performance and long-term storage, which was used for subsequent experiments.

[0032] Step 2: Controllable shaking to encapsulate the target liquid with particles to form a magnetically responsive core-shell structure smooth liquid cake: After obtaining the standardized hydrophobic magnetic iron oxide particles (6) from Step 1, a core-shell structure smooth liquid cake is prepared in a core-shell structure smooth liquid cake generating device. First, a certain amount of the pretreated powder is evenly spread in a smooth liquid cake preparation vessel (7) with a superhydrophobic coating (701) on its surface to form a flat and uniformly thick powder bed. Then, the target liquid is precisely transferred to the central area of ​​the powder bed in small amounts multiple times using a pipette or micro-syringe to prevent the initial spreading area of ​​the liquid from exceeding the coverage of the powder bed. To overcome the problem of poor smooth liquid cake preparation efficiency and consistency caused by manual shaking, this invention preferably fixes the vessel carrying the liquid and powder on a circumferential shaker (8) for standardized shaking. Through system optimization, the shaking frequency of the shaker is set to 150-250 rpm and the shaking time is 30-60 seconds. Under the controllable centrifugal force and periodic shaking, the liquid achieves efficient and uniform rolling in the powder bed, causing the hydrophobic magnetic iron oxide particles to quickly and completely encapsulate the entire gas-liquid interface, thereby forming a core-shell structured smooth liquid cake (9) with stable structure, uniform shell thickness, and magnetic response function. The liquid core (901) is water or cell culture medium. It should be noted that the present invention does not impose any special restrictions on the initial volume of the core-shell structured smooth liquid cake (9). Those skilled in the art can determine the required volume through conventional experiments based on the size and channel complexity of the target open fluidic chip. It can be flexibly adjusted in the range of microliters to milliliters, for example, from 100 μL to 10 mL, all of which are applicable to this method.

[0033] Step 3: Preparation of core-shell structured liquid cakes based on programmed stepped temperature evaporation The smooth liquid cake (9) with magnetic response core-shell structure prepared in step two is transferred to the base (10) of the liquid cake preparation device by a rolling method. The surface of the base is also treated with a superhydrophobic coating (701). Subsequently, a critical draining process is performed to form a stable liquid cake that can be laser-cut. To achieve precise control of this process, avoid potential damage to the liquid cake structure caused by manual draining, and ensure high repeatability, this invention uses a precision evaporation platform (11) to perform a programmed stepped heating evaporation method. Specifically, the base carrying the smooth liquid cake is placed on the platform. The process begins in the initial stabilization stage: the system temperature is set and maintained at 25°C by a precision temperature control module (1101) for about 4 to 8 minutes. This gentle heat input induces the liquid inside the smooth liquid cake to begin to evaporate slowly. The surface magnetic particle layer contracts in a coordinated manner under the action of internal capillary forces, and a uniform and dense supporting wrinkled structure is first formed at the edge area where the bottom of the liquid cake contacts the substrate. This stage aims to achieve a stable drainage ratio of approximately 80% and provide a solid mechanical anchor for the liquid cake, preventing subsequent drastic deformation.

[0034] Subsequently, the system enters the main dehydration stage with stepped heating: the temperature is increased by 5°C in each step, successively reaching 30°C, 35°C, and finally 40°C, with each temperature plateau maintained for 3 to 5 minutes. This stepped heat input strategy ensures uniform heat conduction inside the liquid cake and smooth evaporation of moisture from the surface to the inside, effectively avoiding the adverse situation of surface magnetic particle layer crusting and blocking internal moisture escape due to excessively rapid drying. Throughout the process, the real-time quality monitoring unit (1102) continuously tracks the quality change of the liquid cake, providing accurate data feedback for process control. Finally, the system enters the equilibrium and endpoint determination stage, maintaining at 40°C for a period of time until the mass loss rate of the liquid cake reaches 85% to 98%. At this point, it indicates that the liquid cake has reached the final equilibrium state under the current environmental parameters, and the liquid discharge ratio is precisely controlled between 85% and 98%. A magnetic response wrinkled liquid cake (12) with a longitudinal dimension much smaller than the transverse dimension, in a severely blocked state on the surface, and with a uniform and stable structure has been successfully obtained, laying a solid foundation for subsequent high-quality laser cutting and shaping.

[0035] It should be noted that the initial volume of the smooth liquid cake is one of the key parameters for adjusting the evaporation process. For larger smooth liquid cakes, the holding time of each temperature plateau can be appropriately extended or the number of heating steps can be increased to ensure that the internal moisture is removed sufficiently and uniformly. For smaller smooth liquid cakes, the processing time can be shortened accordingly or a gentler heating program can be used. Those skilled in the art can optimize and adjust the specific temperature parameters and duration through routine experiments based on real-time quality monitoring data.

[0036] Step 4: Liquid cake cutting and channel shaping based on fiber laser The wrinkled liquid cake (12) obtained in step three, together with its supporting base (10), is placed within the processing area of ​​the laser cutting and shaping device. This patent uses a fiber laser (13) to process the liquid cake obtained in step three. The laser has a wavelength of 1064 nanometers, which can be efficiently absorbed by the iron oxide particles. During processing, a lens is used to focus the light to obtain a spot with a diameter of 30-60 micrometers, thereby achieving fine cutting of the surface-mounted iron oxide liquid cake system.

[0037] Before processing with a fiber laser (13), the wrinkled liquid cake (12) needs to be placed at the focal plane of the laser. Since the wrinkled liquid cake (12) is relatively thin, its focal plane can be approximated as being consistent with the plane of the base (10). The height of the base (10) is adjusted by the lifting platform (14) so ​​that the wrinkled liquid cake (12) is positioned at the optimal focal plane of the laser. In order to prevent the iron oxide particles in the liquid cake from being oxidized into weakly magnetic iron oxide due to the high temperature during laser cutting, the present invention needs to introduce a nitrogen protection process under specific processing conditions. Specifically, when the laser power is higher than 15 W, or the liquid cake thickness is greater than 1.5 mm, or the cutting speed is lower than 0.5 mm / s, the nitrogen protection system is activated. The system forms a local inert atmosphere around the laser cutting head, and the nitrogen pressure is controlled within the range of 50 kPa to 100 kPa. This process can not only dissipate the air at the cut and suppress the oxidation reaction, but also avoid the possible disturbance of the liquid cake structure by high pressure gas. Input the preset fluid channel pattern into the laser control system and set the corresponding laser power and scanning speed. Generally, the cutting speed and laser power need to be matched; higher cutting speeds usually require higher laser power. To ensure cutting effectiveness, parameter pre-tests can be conducted in the edge area of ​​the liquid cake.

[0038] During the cutting process, the laser spot moves along a preset path, and its energy is absorbed by the magnetic iron oxide particles on the surface of the liquid cake and converted into heat energy, causing local moisture to evaporate rapidly, thereby achieving cutting and separation. To improve the cutting success rate, especially for complex patterns, it is recommended to use a lead wire design, that is, to have the laser beam cut into the target pattern from the outer edge of the liquid cake. This strategy can more effectively induce material separation than directly starting the cutting on the surface of the liquid cake.

[0039] If the cutting path is interrupted during the cutting process, the following remedial measures can be taken depending on the specific cause: First, particle replenishment method: When the shell density at the cut is too low due to the ablation of magnetic particles, a small amount of similar magnetic powder (6) can be dipped into a micro-tool to replenish the interrupted area in order to restore its heat absorption and vaporization capacity.

[0040] Second, parameter optimization and secondary cutting method: If the cutting is discontinuous due to mismatched laser parameters, the laser power can be appropriately increased or the scanning speed can be reduced, and the laser head can be instructed to retreat a certain distance and then cut along the path again.

[0041] Third, auxiliary dehydration method: If the central area is difficult to cut due to uneven thickness of the liquid cake, the cutting can be suspended, and the liquid cake can be subjected to a short-term secondary programmed step heating evaporation to further reduce its overall liquid content.

[0042] Following the above technical ideas and solutions, the following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0043] Example 1: This embodiment provides a system for fabricating magnetically responsive open-loop fluidic chips, such as... Figure 1 and Figure 2 As shown, the system includes a particle standardization processing device, a core-shell structure smooth liquid cake generation device, a liquid cake preparation device, and a laser cutting and shaping device.

[0044] As a specific embodiment, the particle standardization processing device includes: a muffle furnace (1) for annealing and activating iron oxide powder; an ultrasonic disperser (2) for ultrasonically dispersing the annealed powder; a centrifuge (3) for centrifugally collecting and classifying the dispersion; a solvothermal reaction device (4) for hydrophobic modification of the particles; and a vacuum drying oven (5) for drying the particles to obtain standardized magnetic hydrophobic particles (6).

[0045] As a specific embodiment of this invention, the core-shell structure smooth liquid cake generation device includes: a smooth liquid cake preparation vessel (7) with a superhydrophobic coating (701) on its working surface for carrying a powder bed formed by magnetic particles (6); and a circumferential shaking table (8) for carrying and shaking the smooth liquid cake preparation vessel (7) to cause the particles to wrap the liquid and form a magnetically responsive core-shell structure smooth liquid cake (9).

[0046] As a specific embodiment, the liquid cake preparation device includes: a base (10) made of laser-transparent polystyrene material and having a superhydrophobic coating (701) on its surface, for receiving a smooth liquid cake (9) with a core-shell structure; and a precision evaporation platform (11) integrating a temperature control module (1101) and a quality monitoring unit (1102) for executing a programmed step heating evaporation process to form a wrinkled liquid cake (12).

[0047] As a specific embodiment of this invention, the laser cutting and shaping device includes: a fiber laser engraving device (13), in which a base (10) is provided in the processing area; and a lifting platform (14) for supporting and adjusting the height of the base (10) so that the wrinkled liquid cake (12) is positioned at the optimal focal plane of the laser.

[0048] As a specific solution in this embodiment, the temperature control module (1101) of the precision evaporation platform (11) is capable of executing a multi-stage temperature control program including initial stabilization, step heating and final equilibrium.

[0049] As a specific solution in this embodiment, the real-time quality monitoring unit (1102) is a precision electronic balance, which is used to monitor the quality change of the liquid cake (12) in real time and determine the dehydration endpoint.

[0050] As a specific solution in this embodiment, the laser engraving equipment (13) is a fiber laser system, and its control system supports lead wire cutting path planning.

[0051] As a specific solution in this embodiment, the lifting platform (14) has the ability to make precise height adjustments in the vertical direction.

[0052] Example 2 This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. The method specifically includes the following steps: Step 1: Standardize the iron oxide powder to obtain magnetic hydrophobic particles. Step 1.1, Annealing and impurity removal treatment: Place commercial iron oxide powder (particle size 1-5 μm) in a muffle furnace (1) and anneal for 2 hours in an air atmosphere at 300°C.

[0053] Step 1.2, ultrasonic dispersion treatment: After annealing, the powder is dispersed in anhydrous ethanol and ultrasonically treated for 25 minutes at 500W power using an ultrasonic disperser (2).

[0054] Step 1.3, centrifugal fractionation: The particles were then collected by centrifuging at 8000 rpm for 10 minutes using a centrifuge (3) and redispersed in toluene.

[0055] Step 1.4, hydrophobic modification treatment: Transfer the system to a solvothermal reaction apparatus (4), add 5% by mass of n-octadecyltrimethoxysilane (OTS), and reflux at 80°C for 6 hours under nitrogen protection.

[0056] Step 1.5, Secondary Centrifugation: After the reaction, the particles were collected by magnetic field separation and washed sequentially with toluene and anhydrous ethanol. Fractionation was performed using a stepwise centrifugation method: the particles were centrifuged at 2000 rpm and 5000 rpm for 10 minutes each, and the final precipitate was collected.

[0057] Step 1.6, Drying treatment: Place the obtained precipitate in a vacuum drying oven (5) and dry it at 60°C for 12 hours to obtain standardized magnetic hydrophobic particles (6).

[0058] Step 2: Forming a smooth liquid cake with a magnetically responsive core-shell structure by controlling the shaking to encapsulate the target liquid with particles: Spread 10g of magnetic hydrophobic particles (6) into a smooth liquid cake preparation vessel (7) with a silica superhydrophobic coating (701) on its surface to form a powder bed. Use a pipette to transfer 1 mL of deionized water to the center of the powder bed. Then fix the vessel on a circular shaker (8) and shake it at a frequency of 200 rpm for 45 seconds to form a smooth liquid cake with a magnetically responsive core-shell structure (9).

[0059] Step 3: Dehydrate the smooth liquid cake to form a wrinkled liquid cake through programmed stepped heating evaporation: The core-shell structure smooth liquid cake (9) is rolled and transferred to a base (10) that also has a superhydrophobic coating (701). The base is then placed on a precision evaporation platform (11), and the real-time quality monitoring unit (1102) is turned on. The program is executed through the temperature control module (1101): maintain at 25°C for 6 minutes; then increase the temperature in steps of 5°C each, maintaining at 30°C, 35°C and 40°C for 4 minutes each; finally, maintain at 40°C until the mass loss rate reaches 96%, obtaining a wrinkled liquid cake (12) with a drainage ratio of approximately 96%.

[0060] Step four: Using a fiber laser, the liquid cake is cut and shaped according to a preset pattern to obtain an open fluid channel with magnetic response characteristics: The base (10) with the wrinkled liquid cake (12) is placed in the processing area of ​​the fiber laser engraving equipment (13), and adjusted to the laser focal plane by the lifting platform (14). The preset "dumbbell" shaped channel pattern is input into the control system, the laser power is set to 10 W, the cutting speed is 1 mm / s, and the cutting starts from the edge of the liquid cake using a lead wire. There is no interruption during the cutting process, and a complete "dumbbell" shaped magnetic response open fluid channel is successfully obtained.

[0061] Example 3 This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is essentially the same as that in Embodiment 2, except that step one is different.

[0062] In this embodiment, step one is as follows: Step 1.1, Annealing and impurity removal treatment: Place commercial iron oxide powder (particle size 5-10 μm) in a muffle furnace (1) and anneal at 300°C in an air atmosphere for 2 hours.

[0063] Steps 1.2 and 1.3 are exactly the same as in Example 2.

[0064] Step 1.4: Transfer the system to a solvothermal reaction apparatus (4), add 3% by mass of n-octadecyltrimethoxysilane (OTS), and reflux at 80°C for 4 hours under nitrogen protection.

[0065] Step 1.5, Secondary Centrifugation: After the reaction, the particles were collected by magnetic field separation and washed sequentially with toluene and anhydrous ethanol. Fractionation was performed using a stepwise centrifugation method: the particles were centrifuged at 1500 rpm and 4000 rpm for 15 minutes each, and the final precipitate was collected.

[0066] Step 1.6 is exactly the same as in Example 2.

[0067] Using the method of this embodiment, standardized magnetic hydrophobic particles with relatively large particle size were finally obtained (6).

[0068] Example 4: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is essentially the same as that in Embodiment 2, except that step two is different.

[0069] In this embodiment, step two is as follows: 10g of magnetic hydrophobic particles (6) are spread in a smooth liquid cake preparation vessel (7) with a silica superhydrophobic coating (701) on the surface to form a powder bed. 500 μL of cell culture medium containing HeLa cells is transferred to the center of the powder bed using a pipette. The vessel is then fixed on a circular shaker (8) and shaken at a frequency of 150 rpm for 60 seconds to ensure that the cells are evenly dispersed in the smooth liquid cake and successfully encapsulated, forming a magnetically responsive core-shell structure smooth liquid cake (9).

[0070] Example 5: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is identical to steps one, two, and four of Embodiment 2, except that the evaporation procedure in step three is different.

[0071] In this embodiment, to accommodate a smaller volume of smooth liquid cake (500 μL), the evaporation procedure in step three is optimized as follows: maintain at 25°C for 4 minutes; then gradually increase the temperature to 30°C and 35°C, maintaining each temperature for 3 minutes; finally maintain at 37°C until the end, to obtain a wrinkled liquid cake (12) with a drainage ratio of approximately 93%.

[0072] Example 6: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is identical to steps one, two, and three of Embodiment 2, except that the laser cutting parameters and pattern in step four are different.

[0073] In this embodiment, step four is as follows: The base (10) with the wrinkled liquid cake (12) is placed in the processing area of ​​the fiber laser engraving equipment (13), and adjusted to the laser focal plane by the lifting platform (14). The preset "Y" shaped channel pattern is input into the control system, the laser power is set to 12 W, the cutting speed is 0.8 mm / s, and the cutting is started from the edge of the liquid cake using a lead wire. During the cutting process, the cutting is interrupted in the spiral center area due to particle ablation. Then, the particle replenishment method is adopted, and magnetic particles (6) are dipped into the needle and replenished to the cut. The subsequent cutting is successfully completed, and finally a complete "Y" shaped magnetic response open fluid channel is obtained.

[0074] Example 7: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is essentially the same as that in Embodiment 2, except that step two is different.

[0075] In this embodiment, step two is as follows: 10g of magnetic hydrophobic particles (6) are spread in a smooth liquid cake preparation vessel (7) with a silica superhydrophobic coating (701) to form a powder bed. 2 mL of 85% alcohol aqueous solution is transferred to the center of the powder bed using a pipette. The vessel is then fixed on a circular shaker (8). Due to the low surface tension of alcohol, the vessel is shaken at 250 rpm for 30 seconds during the smooth liquid cake preparation process to ensure rapid encapsulation before liquid evaporation, forming a magnetically responsive core-shell structure smooth liquid cake (9). This embodiment demonstrates the adaptability of this method to liquids with low surface tension.

[0076] Example 8: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is identical to steps one, two, and three of Embodiment 2, except that the cutting strategy and remedial measures in step four are different.

[0077] In this embodiment, step four is as follows: The base (10) with the wrinkled liquid cake (12) is placed in the processing area of ​​the fiber laser engraving equipment (13), and adjusted to the laser focal plane by the lifting platform (14). The preset complex grid-like channel pattern containing multiple intersection nodes is input into the control system, the laser power is set to 15 W, the cutting speed is 1.5 mm / s, and the cutting is started from the edge of the liquid cake using a lead wire. During the cutting process, the cutting is over-cut due to heat accumulation at the intersection nodes, and the cutting is then paused. The wrinkled liquid cake (12) is briefly subjected to secondary step heating and evaporation using an auxiliary dehydration method (maintained at 40°C for 2 minutes) to further reduce the local liquid content. Then, the method is switched to parameter optimization and secondary cutting, and the cutting speed is adjusted to 1 mm / s. The cutting of the fine nodes is successfully completed, and finally a grid-like magnetic response open fluid channel with a complete structure is obtained. This embodiment demonstrates the comprehensive solution capability of the method to deal with highly complex patterns.

[0078] Example 9: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system described in Embodiment 1. This method is identical to steps one, two, and three of Embodiment 2, except that step four is different and specifically designed to demonstrate a nitrogen protection process under high-power processing conditions.

[0079] In this embodiment, step four is as follows: The base (10) with the wrinkled liquid cake (12) is placed in the processing area of ​​the fiber laser engraving equipment (13), and adjusted to the laser focal plane by the lifting platform (14). The preset "grid" shaped channel pattern is input into the control system. To quickly cut this complex pattern, a high laser power of 18 W and a cutting speed of 1.5 mm / s are set. According to the process requirements of step four of this invention, when the laser power is higher than 15 W, the nitrogen protection system needs to be activated. In this embodiment, the nitrogen pressure is set to 60 kPa to form a local inert atmosphere around the laser cutting head. Cutting under these parameters successfully obtained a complex grid-shaped magnetic response open fluid channel with clear contours and no oxidation traces. This embodiment verifies the effectiveness of nitrogen protection in maintaining the magnetic properties of the channel material (Fe3O4) and the cutting quality under high power conditions.

[0080] Example 10: This embodiment presents a method for fabricating a magnetically responsive open fluidic chip based on laser cutting, which is implemented using the system of Embodiment 1. This method is identical to steps one and four of Embodiment 2, except that steps two and three are different, and it is specifically designed to demonstrate a low-speed, fine-cutting process for thick liquid cakes under nitrogen protection.

[0081] In this embodiment, step two is as follows: magnetic hydrophobic particles (6) are spread in a smooth liquid cake preparation vessel (7) with a silica superhydrophobic coating (701) on the surface to form a powder bed. 8 mL of deionized water is transferred to the center of the powder bed using a pipette to form a large-volume magnetically responsive core-shell structure smooth liquid cake (9).

[0082] Step 3 is as follows: Through programmed step heating evaporation treatment (the specific process is the same as in Example 2), a wrinkled liquid cake (12) with a core-shell structure with a thickness of about 2.0 mm and a liquid discharge ratio of about 90% is finally obtained.

[0083] Step four is as follows: The base (10) with a thick wrinkled liquid cake (12) is placed in the processing area of ​​the fiber laser engraving equipment (13), and adjusted to the laser focal plane by the lifting platform (14). The preset "sawtooth" channel pattern is input into the control system, and the laser power is set to 12 W. Since the thickness of the liquid cake is greater than 1.5 mm, a relatively low cutting speed needs to be set to achieve a fine contour. Therefore, the cutting speed is set to 0.3 mm / s. According to the process requirements of step four of the present invention, this condition requires the activation of the nitrogen protection system, and the nitrogen pressure is 100 kPa. Under low-pressure nitrogen protection, a lead wire is used to perform low-speed fine cutting from the edge of the liquid cake, which effectively suppresses the oxidation of the cut edge. There is no interruption during the cutting process, and a regularly shaped sawtooth magnetic response open fluid channel is successfully obtained. This embodiment verifies the necessity and superiority of the nitrogen protection process under the conditions that the liquid cake is thick or the cutting speed is low, resulting in a high risk of heat accumulation.

[0084] In summary, the open-loop fluid chip fabrication method based on magnetic iron oxide powder proposed in this invention overturns the traditional approach of confining fluids with dense solid tubing. It utilizes hydrophobic powder particles to form a blockage-like encapsulation layer at the liquid-gas interface, achieving stable construction of channels with complex shapes, and leverages the permeability of the particle walls to achieve the openness of the channel. The selection of hydrophobic magnetic iron oxide particles imparts magnetic response and other properties to the channel. Combined with laser cutting technology, it achieves automated and precise fabrication, breaking through the shortcomings of existing technologies such as environmental dependence, non-reconfigurability, and functional deficiencies, providing a novel solution for dynamic and intelligent fluid manipulation.

Claims

1. A method for fabricating a magnetic interface open fluidic chip, characterized in that, include: First, magnetite powder is standardized to obtain magnetic hydrophobic particles. Then, the particles are controlled to shake to encapsulate the target liquid and form a smooth liquid cake with a magnetic core-shell structure. Next, the smooth liquid cake is dehydrated to form a wrinkled liquid cake through programmed step heating evaporation. Finally, the wrinkled liquid cake is cut and shaped using a laser to obtain a magnetic interface open fluid chip.

2. The method for fabricating a magnetic interface open fluidic chip as described in claim 1, characterized in that: The method for standardizing magnetite powder to obtain magnetic hydrophobic particles includes: annealing the magnetite powder in air; after annealing, dispersing the powder in anhydrous ethanol and sonicating it; then centrifuging at high speed and collecting the precipitated particles, and redispersing them in toluene; adding n-octadecyltrimethoxysilane to the system and refluxing under nitrogen protection; after the reaction, separating and collecting the particles by magnetic field, and washing them sequentially with toluene and anhydrous ethanol; after washing, performing gradient centrifugation and collecting the precipitate; and drying the precipitate to obtain standardized magnetic hydrophobic particles. The process of forming a smooth liquid cake with a magnetically responsive core-shell structure by encapsulating the target liquid with particles through controlled shaking includes: spreading magnetic hydrophobic particles on a base with a superhydrophobic coating to form a powder bed; adding the target liquid to the center of the powder bed and shaking it to form a smooth liquid cake with a magnetically responsive core-shell structure. Dehydrating a smooth liquid cake to form a wrinkled liquid cake through programmed stepped temperature evaporation includes: rolling a core-shell structured smooth liquid cake onto a base with a superhydrophobic coating on its surface, and using segmented temperature step-by-step treatment to obtain a wrinkled liquid cake. The method of using laser to cut and shape a wrinkled liquid cake to obtain a magnetic interface open fluid chip includes: placing a base carrying the wrinkled liquid cake in the processing area of ​​a fiber laser engraving device and adjusting it to the laser focal plane; inputting a preset channel pattern into the control system and starting to cut from the edge of the wrinkled liquid cake; after cutting, obtaining an open fluid channel with magnetic response characteristics, thus producing a magnetic interface open fluid chip.

3. The method for fabricating a magnetic interface open fluidic chip as described in claim 2, characterized in that: The annealing temperature is 200–400℃, and the time is 1–3 hours; The ultrasonic treatment power is 400-600W, and the time is 20-30 minutes; The high-speed centrifugation speed is 8000-12000 rpm, and the time is 5-15 minutes; The reflux reaction temperature is 70–90°C, and the time is 4–6 hours; The gradient centrifugation conditions are as follows: first centrifuge at 1500-2000 rpm for 10-15 minutes, then centrifuge at 4000-5000 rpm for 10-15 minutes.

4. The method for fabricating a magnetic interface open fluidic chip as described in claim 2, characterized in that, The amount of n-octadecyltrimethoxysilane added is 3% to 5% of the particle mass.

5. The method for fabricating a magnetic interface open fluidic chip as described in claim 2, characterized in that, The shaking frequency is 150–250 rpm, and the duration is 30–60 seconds.

6. The method for fabricating a magnetic interface open fluidic chip as described in claim 2, characterized in that, The temperature step-by-step treatment is as follows: first, maintain at 25°C for 4 to 6 minutes; then increase the temperature in steps of 5°C per stage, maintaining for 3 to 4 minutes after each increase; and maintain at a final temperature of 37 to 40°C until the mass loss rate reaches 85 to 98%.

7. The method for fabricating a magnetic interface open fluidic chip as described in claim 2, characterized in that, The laser wavelength used for cutting is 1064 nanometers.

8. The method for fabricating a magnetic interface open fluidic chip as described in claim 2, characterized in that, When cutting wrinkled liquid cakes, the laser power is 10-18 W and the cutting speed is 0.3-1.5 mm / s.

9. The method for fabricating a magnetic interface open fluidic chip as described in claim 8, characterized in that, When the laser power is greater than 15 W, or the thickness of the wrinkled liquid cake is greater than 1.5 mm, or the cutting speed is less than 0.5 mm / s, cutting is carried out in a nitrogen atmosphere with a nitrogen pressure of 50–100 kPa.

10. A magnetic interface open fluidic chip prepared by the method as described in any one of claims 1 to 9.

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