Quaternary paddle unplug micro robot and magnetic field driven unplug micro robot system

Abstract

The application discloses a four-stage paddle thrombus-removing micro robot, a preparation method and a magnetic field driving thrombus-removing micro robot system, relates to the technical field of micro robots, and comprises a conical drill bit, a main straight rod and a four-stage paddle group, wherein the conical drill bit is made of a biodegradable material; the bottom of the conical drill bit is connected with the main straight rod; the main straight rod is internally provided with a thrombolytic drug; the four-stage paddle group is arranged on the outer circumferential surface of the main straight rod in an axial direction; the paddle group comprises three paddle blades which are centrally symmetrical to the axis of the main straight rod; the paddle blades in the adjacent two-stage paddle groups are arranged in a staggered manner; the paddle blades are of a round head structure; the thickness of the paddle blades gradually increases from outside to inside; and the surface of the micro robot is coated with a magnetic film and is subjected to directional magnetization treatment. The application can obtain strong movement ability and stable movement state under the accurate control of a movement system, realizes intravascular drilling and crushing of a thrombus, and can biodegrade and release the thrombolytic drug after surgery, so as to solve the problem of downstream vascular embolism after drilling.

Description

Technical Field

[0001] This invention relates to the field of microrobot technology, and in particular to a four-stage propeller-driven thrombus-clearing microrobot and a magnetic field-driven thrombus-clearing microrobot system. Background Technology

[0002] Myocardial infarction and cerebral infarction are highly fatal diseases caused by thrombosis resulting from abnormal blood clots blocking blood vessels. Due to the narrow, closed, and complex nature of the human vascular system, traditional treatments are risky and ineffective. Current thrombosis treatments mainly involve open surgery on the affected area and the administration of thrombolytic and anticoagulant drugs to remove the clot. Open surgery is highly invasive, with significant drawbacks such as high postoperative infection risk, slow recovery, and long hospital stays, and it also lacks personalized and humane treatment plans. Drug therapy almost always carries the risk of bleeding, has limited applicability, and is expensive. Therefore, there is an urgent need to develop a highly efficient and low-damage treatment method for myocardial and cerebral thrombosis. Currently, microrobot technology offers a new approach to thrombosis treatment. Microrobots can enter the body non-invasively and perform precise operations in narrowed blood vessels or tissues. For example, existing microrobots typically carry drugs to remove clots. However, these methods may have limitations, such as low operational precision, large robot size, and inability to overcome blood flow resistance. Therefore, a novel microrobot design is needed to improve the effectiveness and efficiency of clot removal. This microrobot needs to possess high mobility, precise manipulation capabilities, and the ability to adapt to different blood vessel sizes and shapes. Simultaneously, it should also have a small size and good biocompatibility to ensure safe application within the human body.

[0003] Taking commonly used magnetically controlled helical microrobots (such as patent CN113696996A) as an example, these robots can move to the location of thrombi in a patient's blood vessels under the influence of an external rotating magnetic field. Utilizing the strong torque generated by their own rotation, they continuously drill through the thrombus, gradually creating openings and diluting viscous substances, ultimately achieving the goal of penetrating the thrombus. However, in practical applications, these helical microrobots still have significant drawbacks, mainly in the following aspects: First, their helical structure, especially the single-helix structure, leads to unstable motion during rotation, making them prone to drifting and shaking. The small contact area results in insufficient rotational torque and movement speed, making it difficult to effectively penetrate thrombi. Second, under current technological conditions, to achieve the magnetically controlled process, the microrobots are made of materials that are difficult to degrade and absorb, further increasing the burden on patients' postoperative recovery. Third, when using helical microrobots for thrombus treatment to drill through thrombi, the upstream thrombus is broken up, and the broken blood clots can easily cause downstream capillary blockage, leading to pulmonary embolism, etc. Summary of the Invention

[0004] The purpose of this invention is to provide a four-stage paddle-driven thrombectomy microrobot and a magnetic field-driven thrombectomy microrobot system to solve the problems existing in the prior art. Under the precise control of the motion system, it can obtain strong motion ability and stable motion state, realize intravascular drilling and fragmentation of thrombi, and the microrobot can biodegrade and release thrombolytic drugs after the operation to solve the problem of downstream vascular embolism after drilling.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] This invention provides a four-stage paddle-driven thrombolytic microrobot, comprising a conical drill bit made of biodegradable material, a main body rod, and a four-stage paddle assembly. The bottom of the conical drill bit is connected to the main body rod, which contains thrombolytic drugs. The four-stage paddle assembly is arranged axially on the outer circumference of the main body rod. Each paddle assembly includes three paddles that are centrally symmetrical about the axis of the main body rod. The paddles in adjacent paddle assemblies are staggered. The paddles have rounded heads and their thickness gradually increases from the outside to the inside. The surface of the microrobot is coated with a magnetic film and subjected to directional magnetization.

[0007] Preferably, the height of the conical drill bit is 22-28 μm, the bottom diameter is 12-18 μm, and the apex angle is 2×arctan3 / 14-2×arctan9 / 22; the length of the main straight rod is 140-180 μm, and the bottom diameter is 12-18 μm.

[0008] Preferably, the fourth-stage blade assembly is arranged axially on the outer circumference of the main body straight rod, starting from a distance of 4 to 6 μm from the bottom surface of the conical drill bit.

[0009] Preferably, the blade has a width of 22-28 μm, a blade edge distance of 30-35 μm from the center, an opening angle of 100-140 degrees, a pitch of 80-100 μm, and a 1 / 3 turn; the spacing between blades in adjacent blade groups is 8-12 μm; the outer thickness of the blade is 1.2-1.8 μm, and the inner thickness is 2.2-2.8 μm.

[0010] This invention also provides a method for manufacturing the above-described four-stage propeller-driven thrombus-clearing microrobot, comprising:

[0011] Robot body manufacturing: The robot body was prepared by copolymerization of methacrylic anhydride gelatin, sodium 4-styrene sulfonate monomer, and dihydroxypropyl 2,3-methacrylate monomer using two-photon polymerization laser printing.

[0012] Magnetic film coating on robot surface: A magnetic film composed of magnetite particles encapsulated in polyvinylpyrrolidone is coated on the robot surface using a chemical bonding method.

[0013] Robot magnetization: Directional magnetization of microrobots using a unipolar uniform magnetization system.

[0014] Preferably, the manufacturing of the robot body includes the following steps:

[0015] (1) Preparation of methacrylic anhydride-modified gelatin:

[0016] S1: Add gelatin to PBS phosphate buffer solution, heat and stir until the gelatin is completely dissolved;

[0017] S2: Add the MA solution dropwise to the gelatin solution while stirring continuously during the addition process; after stirring is complete, add PBS phosphate buffer solution to dilute and continue stirring;

[0018] S3: After terminating the reaction, put the mixed solution from S2 into a dialysis bag and dialyze it in ultrapure water at room temperature;

[0019] S4: After dialysis, the dialysis solution is placed in a beaker and heated in a water bath. It is then filtered while hot using a microporous membrane. The resulting filtrate is freeze-dried to obtain methacrylic anhydride gelatin, which is then dried at low temperature and stored for later use.

[0020] (2) Copolymerization of sodium 4-styrene sulfonate monomer, dihydroxypropyl 2,3-methacrylate monomer and methacrylic anhydride gelatin:

[0021] S1: Place the prepared methacrylic anhydride gelatin in PBS phosphate buffer, and after reaching equilibrium, dry it at a constant temperature until constant weight, and set aside for later use;

[0022] S2: Mix and dissolve sodium 4-styrenesulfonate monomer, dihydroxypropyl 2,3-methacrylate monomer and crosslinking initiator, and adjust the pH of the solution to be consistent with the PBS phosphate buffer in S1.

[0023] S3: Immerse the dried GelMA gel treated in step S1 in the solution obtained in step S2 at a temperature below 60°C to obtain the sample required for three-dimensional processing, and store it at low temperature for later use.

[0024] (3) Robotic 3D structure processing:

[0025] S1: Applying photoresist: Use a micropipette to pick up the photoresist and drop it onto the center of the ultra-clean microscope coverslip;

[0026] S2: Pre-baking: Pre-baking the hot plate;

[0027] S3: Processing: After collimating the optical path, place the sample on the three-dimensional piezoelectric platform, locate the focal plane, and select appropriate laser energy to perform microstructure scanning processing;

[0028] S4: Development: Wipe the oil off the back of the sample, clamp it with a clip, mark it, and place it in n-propanol for development. The unpolymerized parts are washed away, leaving the printed three-dimensional microstructure.

[0029] Preferably, the magnetic film coating on the robot surface includes the following steps:

[0030] S1: Introduce the magnetic particles of iron oxide coated with polyvinylpyrrolidone into deionized water and mix them to form a magnetic solution mother liquor;

[0031] S2: Use a pipette to draw a drop of mother liquor onto the microrobot body, place it on a shaker at room temperature and mix well to obtain a microrobot coated with magnetic particles.

[0032] Preferably, the robot magnetization includes the following steps:

[0033] S1: Place the robot at an angle appropriate to the generated magnetic field in the central region of the single-axis electromagnet system;

[0034] S2: A uniform magnetic field is generated by passing an electric current through it. The microrobot is placed in the magnetization area for an appropriate time to be magnetized.

[0035] This invention also provides a magnetic field-driven thrombectomy microrobot system, including the aforementioned four-stage propeller thrombectomy microrobot, as well as a host computer, a slave computer, a driver, and an eight-stage electromagnetic coil. The user inputs the required magnetic field data through the user interface of the host computer, which calculates and converts it into corresponding current information and transmits it to the slave computer. The slave computer converts the received current signal into a PWM signal and transmits it to the driver. The driver converts the received signal into a corresponding current and outputs it to the eight-stage electromagnetic coil. The eight-stage electromagnetic coil generates different types of magnetic fields to achieve motion control of the four-stage propeller thrombectomy microrobot.

[0036] The present invention achieves the following technical effects compared to the prior art:

[0037] The present invention provides a four-stage paddle-driven thrombolytic microrobot, its preparation method, and a magnetic field-driven thrombolytic microrobot system. The main body material of the thrombolytic microrobot is a biodegradable material coated with a magnetic film. Thrombolytic drugs are placed inside the main body rod. This allows it to highly adapt to the living biological environment and avoid biological rejection while obtaining magnetic driving force. Post-operatively, the microrobot can biodegrade and release thrombolytic drugs to solve the problem of downstream vascular embolism after drilling. A four-stage paddle assembly is set on the main body rod, with the four-stage paddle assembly arranged axially on the outer circumferential surface of the main body rod. The paddle assembly includes a main body... The straight rod has three centrally symmetrical blades on its axis. The blades in adjacent blade groups are arranged in an alternating pattern, which significantly increases the contact area between the robot body and the liquid environment. This ensures the stability of its rotation process and avoids phenomena such as drifting and shaking. It also has greater rotational torque and moving speed, which can generate enough force to "drill" open blood clots. Under the precise control of the motion system, it can obtain strong motion ability and stable motion state. In addition, each blade is designed with a rounded head to minimize the chance of the blade scratching the inner wall of the blood vessel during forward movement. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic diagram of the structure of the four-stage propeller-driven thrombus-clearing microrobot provided by the present invention;

[0040] Figure 2 A cross-sectional schematic diagram of the four-stage blade thrombus clearing microrobot provided by the present invention;

[0041] Figure 3 The design flowchart of the magnetic field-driven thrombectomy microrobot system provided by the present invention;

[0042] Figure 4 The control principle diagram of the magnetic field driven thrombus clearing microrobot system provided by the present invention;

[0043] In the diagram: 1-conical drill bit, 2-main body rod, 3-blade assembly, 4-blade. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely 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.

[0045] The purpose of this invention is to provide a four-stage paddle-driven thrombectomy microrobot and a magnetic field-driven thrombectomy microrobot system to solve the problems existing in the prior art. Under the precise control of the motion system, it can obtain strong motion ability and stable motion state, realize intravascular drilling and fragmentation of thrombi, and the microrobot can biodegrade and release thrombolytic drugs after the operation to solve the problem of downstream vascular embolism after drilling.

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0047] like Figures 1-2 As shown, this embodiment provides a four-stage blade thrombolytic microrobot, including a conical drill bit 1 made of biodegradable material, a main body rod 2, and a four-stage blade assembly 3; the bottom of the conical drill bit 1 is connected to the main body rod 2, and the main body rod 2 contains thrombolytic drugs; the four-stage blade assembly 3 is arranged axially on the outer circumferential surface of the main body rod 2, and the blade assembly 3 includes three blades 4 that are centrally symmetrical about the axis of the main body rod 2; the blades 4 in adjacent blade assemblies 3 are arranged alternately; the blades 4 have a round head structure; the thickness of the blades 4 gradually increases from the outside to the inside; the surface of the microrobot is coated with a magnetic film and subjected to directional magnetization treatment.

[0048] In this embodiment, the height of the conical drill bit 1 is 22–28 μm, preferably 25 μm, the bottom diameter is 12–18 μm, preferably 15 μm, and the apex angle is 2×arctan3 / 14–2×arctan9 / 22, preferably 2×arctan3 / 10; the length of the main body rod 2 is 140–180 μm, preferably 160 μm, and the bottom diameter is 12–18 μm, preferably 15 μm. The four-stage blade assembly 3 is arranged axially on the outer circumference of the main body rod 2, starting from a distance of 4–6 μm, preferably 5 μm, from the bottom surface of the conical drill bit 1.

[0049] In this embodiment, the width of the blade 4 is 22-28 μm, preferably 25 μm, the distance from the blade edge to the center is 30-35 μm, preferably 32.5 μm, the opening angle is 100-140 degrees, preferably 120 degrees, and the pitch is 80-100 μm, preferably 90 μm, 1 / 3 turn; the spacing between the blades 4 in adjacent blade groups 3 is 8-12 μm, preferably 10 μm; the outer thickness of the blade 4 is 1.2-1.8 μm, preferably 1.5 μm, and the inner thickness is 2.2-2.8 μm, preferably 2.5 μm.

[0050] The four-stage paddle-type thrombectomy microrobot provided in this embodiment is much smaller than the average diameter of human cardiovascular vessels, enabling minimally invasive surgery. It can penetrate deep into the tiny blood vessels of the heart and brain, breaking up thrombi to a state where they can flow with the blood. The robot's main body is made of biodegradable materials and coated with a magnetic film, allowing it to highly adapt to the living environment and avoid biological rejection while obtaining magnetic driving force. Post-operatively, the microrobot can biodegrade and release thrombolytic drugs to address downstream vascular embolism after drilling. The conical drill bit 1 has a height (25μm), a base diameter (15μm), and an apex angle (2×arctan3 / 10), which maximizes the movement speed and drilling efficiency on thrombi. The main body straight rod 2 has a length (160μm), a base outer diameter (15μm), and an inner diameter (12.5μm), reducing the overall mass of the microrobot and ensuring precision. To achieve motion control and improve movement speed, the four-stage, three-bladed propeller has a high propulsion effect under the above parameters. The staggered arrangement of the blades in adjacent stages also improves the robot's movement speed. Each stage of three blades is centrally symmetrical about the main body rod. Each blade 4 has a rounded head design and a thickness of 1.5μm (outer)-2.5μm (inner). By setting the fan-blade structure, the contact area between the robot body and the liquid environment is significantly increased, thereby ensuring the stability of its rotation process and avoiding phenomena such as drifting and shaking. It also has a greater rotational torque and movement speed, thus generating enough force to "drill" open blood clots. Furthermore, the rounded head design of each blade 4 minimizes the chance of the blade 4 scratching the inner wall of the blood vessel during forward movement. The hollow part inside the main body rod 2 is a cylindrical structure with a length of (12μm) and a diameter of (12.5μm), maximizing the drug capacity and minimizing drug loss during robot movement. Low molecular weight heparin (LMWH) can be coated inside the main straight rod 2 to dissolve the blood clots drilled by the robot upstream and prevent them from causing embolism downstream.

[0051] In this embodiment, the four-stage, three-bladed propellers are arranged starting 5 μm below the conical drill bit 1. Each blade 4 has a width of 25 μm, a blade edge distance of 32.5 μm from the center, an angle of 120 degrees, and a pitch of 90 μm (1 / 3 turn). The spacing between different stages of blades 4 is 10 μm, with adjacent stages of blades 4 arranged alternately. At a microscale, the inertial force of the magnetically controlled microrobot in liquid is negligible, and it is mainly affected by viscous drag. Therefore, to achieve high-speed movement in liquid environments, the shape of the microrobot needs careful design. Considering that a helical structure can generate rotational motion by breaking time symmetry, it is one of the most ideal motion models in low Reynolds number environments. Therefore, in this embodiment, a helical structure composed of multiple blades is chosen for application in the task of thrombus removal by the magnetically controlled microrobot. This blade design allows the robot to rotate and move freely inside the blood vessel, improving the robot's forward speed and maneuverability.

[0052] A method for manufacturing the above-mentioned four-stage propeller-driven thrombus-clearing microrobot includes:

[0053] Robot body manufacturing: It is prepared by two-photon polymerization laser printing using copolymerized gelatin (GelMA) and sodium 4-styrene sulfonate (SS) monomers and dihydroxypropyl 2,3-methacrylate (DM) monomers.

[0054] Magnetic film coating on robot surface: A magnetic film composed of PVP@Fe3O4 (magnetic particles of iron oxide encapsulated in polyvinylpyrrolidone) is coated on the robot surface using a chemical bonding method. These magnetic particles have good dispersibility in water.

[0055] Robot magnetization: Directional magnetization of microrobots using a unipolar uniform magnetization system.

[0056] The manufacturing of the robot body includes the following steps:

[0057] (1) Preparation of GelMA gel:

[0058] S1: Accurately weigh 10g of gelatin, add 100mL of freshly prepared PBS phosphate buffer solution, heat the gelatin mixture at 60℃ and stir until the gelatin is completely dissolved;

[0059] S2: When the gelatin is dissolved into a viscous liquid without particles, add 8 mL of MA solution dropwise to the gelatin solution at a rate of 1 mL / min, maintain the temperature at 50℃ during the dropwise addition, and continue stirring for 3 hours; after stirring is complete, add 4 times the volume of PBS phosphate buffer solution to dilute, and continue stirring for 10 minutes.

[0060] S3: After terminating the reaction, the mixed solution in S2 was placed into a dialysis bag and dialyzed in ultrapure water at room temperature for 7 days, with the ultrapure water being changed every 12 hours.

[0061] S4: After dialysis, the dialysis solution is placed in a beaker and heated in a 60°C water bath for 10 minutes. It is then filtered while hot using a microporous membrane with a pore size of 0.22 μm. The resulting filtrate is freeze-dried to obtain GelMA gel, which is then dried at low temperature and stored for later use.

[0062] (2) Copolymerization of sodium 4-styrenesulfonate monomer, dihydroxypropyl 2,3-methacrylate monomer and GelMA:

[0063] S1: Take an appropriate amount of the prepared GelMA gel, place it in PBS phosphate buffer at pH 8 for a sufficient time until it reaches equilibrium, and then dry it at 60℃ until it reaches constant weight for later use.

[0064] S2: Accurately weigh a certain amount of sodium 4-styrene sulfonate (SS) monomer, dihydroxypropyl 2,3-methacrylate (DM) monomer, and crosslinking initiator, and mix and dissolve them. Adjust the pH of the solution to be consistent with that of PBS phosphate buffer in S1; to prevent the copolymerization effect of GelMA gel and sodium 4-styrene sulfonate monomer and dihydroxypropyl 2,3-methacrylate monomer solution from being affected by pH inconsistency.

[0065] S3: After immersing the dried GelMA gel treated in step S1 in the solution obtained in step S2 for a sufficient time at a temperature below 60°C, the sample required for three-dimensional processing is obtained and stored at low temperature for later use. The temperature is below 60°C to prevent the properties of the gel from changing due to heat.

[0066] (3) Robotic 3D structure processing:

[0067] S1: Coating: Use a micropipette to pick up SZ2080 photoresist and drop it onto the center of the ultra-clean microscope coverslip;

[0068] S2: Pre-baking: Raise the hot plate temperature to 60°C and bake for 10 minutes (to prevent bubbles from forming), then raise the temperature to 100°C and bake for 40 minutes;

[0069] S3: Processing: After collimating the optical path, place the sample on the three-dimensional piezoelectric platform, locate the focal plane, and select appropriate laser energy to perform microstructure scanning processing;

[0070] S4: Development: Wipe the oil off the back of the sample, clamp it with a clip, mark it, and place it in n-propanol for development for 1 hour. The unpolymerized parts are washed away, leaving the printed three-dimensional microstructure.

[0071] The magnetic film coating on the robot surface includes the following steps:

[0072] S1: Weigh 1g of magnetic particles PVP@Fe3O4 (magnetic particles of iron oxide coated with polyvinylpyrrolidone) and introduce them into 10mL of deionized water. Mix them at high speed for 60s in a high-speed gyroscope to form a 1% magnetic solution stock solution.

[0073] S2: When using, use a pipette to draw the mother liquor and drop it onto the microrobot body, then place it on a shaker at room temperature to mix and obtain a microrobot coated with magnetic particles.

[0074] The robot magnetization process includes the following steps:

[0075] S1: Place the robot at an angle appropriate to the generated magnetic field in the central region of the single-axis electromagnet system;

[0076] S2: A uniform magnetic field can be generated by passing in a current of a certain magnitude. The microrobot can be placed in the magnetized area for an appropriate time.

[0077] like Figures 3-4 As shown, this embodiment provides a magnetic field-driven thrombectomy microrobot system, including the aforementioned four-stage propeller thrombectomy microrobot, as well as a host computer, a slave computer, a driver, and an eight-stage electromagnetic coil. The user inputs the required magnetic field data through the host computer's user interface, which calculates and converts it into corresponding current information, transmitting it to the slave computer. The slave computer converts the received current signal into a PWM signal and transmits it to the driver. The driver converts the received signal into a corresponding current output to the eight-stage electromagnetic coil. The eight-stage electromagnetic coil generates different types of magnetic fields, achieving motion control of the four-stage propeller thrombectomy microrobot.

[0078] The specific operation steps of the above-mentioned magnetic field-driven thrombus-clearing microrobot system are as follows:

[0079] S1: The user inputs commands on the user UI interface using the operating terminal, providing the desired magnetic field data and behavioral instructions;

[0080] S2: The instructions input by the user will be processed by the host computer and output as digital signals, which will then be transmitted to the connected circuit board.

[0081] S3: The circuit board will convert the signal into a current signal and output it to the power amplifier. The power amplifier will transmit the amplified current signal to the lower-level machine and convert it into a PWM signal for subsequent electromagnetic coil control.

[0082] S4: After the lower-level machine transmits the PWM signal to the driver, the driver will output current to the eight-pole electromagnetic coil to control the generation of different types of magnetic fields;

[0083] S5: The generated magnetic field will act on the microrobot, controlling its movement;

[0084] S6: Users can observe the movement of the microrobot through the microscopic observation platform, and make further adjustments on the operating terminal based on the feedback of the movement to ensure the stability and accuracy of the microrobot's movement.

[0085] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A four-stage propeller-driven thrombus-clearing microrobot, characterized in that: The device includes a tapered drill bit made of biodegradable material, a main straight rod, and a four-stage blade assembly. The bottom of the tapered drill bit is connected to the main straight rod, which contains thrombolytic drugs. The four-stage blade assembly is arranged axially on the outer circumference of the main straight rod. Each blade assembly includes three blades that are centrally symmetrical about the axis of the main straight rod. The blades in adjacent blade assemblies are staggered. The blades have rounded heads and their thickness gradually increases from the outside to the inside. The surface of the microrobot is coated with a magnetic film and subjected to directional magnetization.

2. The four-stage propeller-driven thrombus-clearing microrobot according to claim 1, characterized in that: The height of the conical drill bit is 22-28 μm, the bottom diameter is 12-18 μm, and the apex angle is 2×arctan3 / 14-2×arctan9 / 22; the length of the main straight rod is 140-180 μm, and the bottom diameter is 12-18 μm.

3. The four-stage propeller-driven thrombus-clearing microrobot according to claim 1, characterized in that: The fourth-stage blade assembly is arranged axially on the outer circumference of the main straight rod, starting from a distance of 4-6 μm from the bottom surface of the conical drill bit.

4. The four-stage propeller-driven thrombus-clearing microrobot according to claim 1, characterized in that: The blade has a width of 22–28 μm, a blade edge distance of 30–35 μm from the center, an opening angle of 100–140 degrees, a pitch of 80–100 μm, and a 1 / 3 turn; the spacing between blades in adjacent blade groups is 8–12 μm; the outer thickness of the blade is 1.2–1.8 μm, and the inner thickness is 2.2–2.8 μm.

5. A method for manufacturing a four-stage propeller-driven thrombus-clearing microrobot as described in any one of claims 1 to 4, characterized in that, include: Robot body manufacturing: The robot body was prepared by copolymerization of methacrylic anhydride gelatin, sodium 4-styrene sulfonate monomer, and dihydroxypropyl 2,3-methacrylate monomer using two-photon polymerization laser printing. Magnetic film coating on robot surface: A magnetic film composed of magnetite particles encapsulated in polyvinylpyrrolidone is coated on the robot surface using a chemical bonding method. Robot magnetization: Directional magnetization of microrobots using a unipolar uniform magnetization system.

6. The method for manufacturing the four-stage propeller-driven thrombus-clearing microrobot according to claim 5, characterized in that: The manufacturing of the robot body includes the following steps: (1) Preparation of methacrylic anhydride-modified gelatin: S1: Add gelatin to PBS phosphate buffer solution, heat and stir until the gelatin is completely dissolved; S2: Add the MA solution dropwise to the gelatin solution while stirring continuously during the addition process; after stirring is complete, add PBS phosphate buffer solution to dilute and continue stirring; S3: After terminating the reaction, put the mixed solution from S2 into a dialysis bag and dialyze it in ultrapure water at room temperature; S4: After dialysis, the dialysis solution is placed in a beaker and heated in a water bath. It is then filtered while hot using a microporous membrane. The resulting filtrate is freeze-dried to obtain methacrylic anhydride gelatin, which is then dried at low temperature and stored for later use. (2) Copolymerization of sodium 4-styrene sulfonate monomer, dihydroxypropyl 2,3-methacrylate monomer and methacrylic anhydride gelatin: S1: Place the prepared methacrylic anhydride gelatin in PBS phosphate buffer, and after reaching equilibrium, dry it at a constant temperature until constant weight, and set aside for later use; S2: Mix and dissolve sodium 4-styrenesulfonate monomer, dihydroxypropyl 2,3-methacrylate monomer and crosslinking initiator, and adjust the pH of the solution to be consistent with the PBS phosphate buffer in S1. S3: Immerse the dried GelMA gel treated in step S1 in the solution obtained in step S2 at a temperature below 60°C to obtain the sample required for three-dimensional processing, and store it at low temperature for later use. (3) Robotic 3D structure processing: S1: Applying photoresist: Use a micropipette to pick up the photoresist and drop it onto the center of the ultra-clean microscope coverslip; S2: Pre-baking: Pre-baking the hot plate; S3: Processing: After collimating the optical path, place the sample on the three-dimensional piezoelectric platform, locate the focal plane, and select appropriate laser energy to perform microstructure scanning processing; S4: Development: Wipe the oil off the back of the sample, clamp it with a clip, mark it, and place it in n-propanol for development. The unpolymerized parts are washed away, leaving the printed three-dimensional microstructure.

7. The method for manufacturing a four-stage propeller-driven thrombus-clearing microrobot according to claim 5, characterized in that: The magnetic film coating on the robot surface includes the following steps: S1: Introduce the magnetic particles of iron oxide coated with polyvinylpyrrolidone into deionized water and mix them to form a magnetic solution mother liquor; S2: Use a pipette to draw a drop of mother liquor onto the microrobot body, place it on a shaker at room temperature and mix well to obtain a microrobot coated with magnetic particles.

8. The method for manufacturing the four-stage propeller-driven thrombus-clearing microrobot according to claim 5, characterized in that: The robot magnetization process includes the following steps: S1: Place the robot at an angle appropriate to the generated magnetic field in the central region of the single-axis electromagnet system; S2: A uniform magnetic field is generated by passing an electric current through it. The microrobot is placed in the magnetization area for an appropriate time to be magnetized.

9. A magnetic field-driven thrombus-clearing microrobot system, characterized in that: The four-stage propeller-driven thrombus-clearing microrobot, as described in any one of claims 1 to 4, further includes a host computer, a slave computer, a driver, and an eight-stage electromagnetic coil. The user inputs the required magnetic field data through the user interface of the host computer, which calculates and converts it into corresponding current information and transmits it to the slave computer. The slave computer converts the received current signal into a PWM signal and transmits it to the driver. The driver converts the received signal into a corresponding current and outputs it to the eight-stage electromagnetic coil. The eight-stage electromagnetic coil generates different types of magnetic fields to achieve motion control of the four-stage propeller-driven thrombus-clearing microrobot.

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