Double-cone DNA chain-shaped magnetic micro-robot structure and driving method

Abstract

The application discloses a double-cone DNA chain-shaped magnetic micro-robot structure and a driving method. The micro-robot comprises a chain-shaped main body extending along a central axis, the chain-shaped main body is composed of two spiral main chains and a transverse connection sequence, the transverse connection sequence connects the two spiral main chains into a DNA chain-shaped structure, and an envelope circumscribing the micro-robot main body structure is double-cone-shaped. A magnetic functional layer and a biocompatible layer are sputtered on the outer surface of the micro-robot in sequence. The magnetic functional layer is magnetized to form a fixed magnetization direction with a preset misalignment angle with the central axis, so that the micro-robot can realize spiral propulsion under the action of an externally applied uniform rotating magnetic field. The propulsion direction can be switched by changing the rotating axis angle of the rotating magnetic field, so that the tail part can be used as the head part for propulsion in the return process, and the whole turning operation is avoided. The structure takes into account the drag reduction and attitude stability, and is suitable for micro-fluidic control and biomedical scenes.

Description

Technical Field

[0001] This invention belongs to the field of microrobots, specifically relating to a biconical DNA chain magnetic microrobot structure and its driving method. Background Technology

[0002] With advancements in genetic engineering, microfluidic chips, sensing, targeted therapy, and environmental monitoring, the demand for microrobots is increasing. Achieving high-precision, low-damage active manipulation within microscale spaces such as blood vessels, cavities, and interstitial spaces has become a research hotspot. Existing magnetically driven helical microrobots mostly employ solid or semi-solid structures such as cylindrical helices or single-cone helices, driven by rotating magnetic fields. However, as the scale decreases, these structures face challenges such as narrowing processing windows and difficulty in stabilizing fine features. Furthermore, the high proportion of solid material leads to increased inertia and fluid resistance, hindering efficient propulsion and precise manipulation in low Reynolds number environments. In complex fluid environments, microrobots are susceptible to changes in viscous drag, local flow field disturbances, and boundary effects, exhibiting phenomena such as yaw, sideslip, or trajectory drift. Traditional single-shaped helical propulsion bodies lack sufficient attitude stability, especially during turns, narrow passages, or near-wall movements, easily leading to attitude instability and path error accumulation, thus affecting motion controllability and mission reliability. To improve structural strength and motion stability, some solutions employ thickened helical blades, added support beams, or multi-material composite structures. However, these typically introduce additional fluid resistance and reduce propulsion efficiency. Furthermore, improper internal support structure arrangement can cause geometric asymmetry, leading to uneven magnetic moment distribution and fluid forces, thus exacerbating attitude fluctuations during motion and limiting the application of microrobots in precise path tracking and long-distance stable motion. Magnetic-driven microrobots require a stable magnetic response layer on the structural surface to generate sufficient magnetic moments. However, current methods lack synergistic optimization between magnetic layer fabrication and structural design. It is difficult to simultaneously ensure the uniformity of magnetic material coverage, adhesion strength, and dimensional consistency on the microstructure surface. Moreover, the introduction of the magnetic layer may alter the equivalent size and local surface roughness of the microstructure, thereby affecting fluid resistance and propulsion performance. Therefore, a microrobot structural design scheme that balances structural symmetry, lightweight reinforcement, and magnetic response realization is urgently needed. Summary of the Invention

[0003] This invention provides a biconical DNA chain-like magnetic microrobot, which simultaneously possesses good structural symmetry and fixed-distance reinforcement capabilities. The main structure of the microrobot is formed by two helical main chains and transverse connecting sequences. While ensuring overall torsional stiffness and structural stability, it is beneficial to promote fluid adhesion and inhibit flow separation to improve the movement speed of the microrobot. Furthermore, a magnetic functional layer and a biocompatible layer are sputtered on the surface of the microrobot structure to impart stable magnetic response and biocompatibility. Under the action of an external rotating magnetic field, it can generate a controllable magnetic moment and achieve stable rotational propulsion, thereby improving the attitude stability and environmental adaptability during the movement process.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: the magnetic microrobot structure includes a microrobot main structure, a magnetic functional layer, and a biocompatible layer. The microrobot main structure includes two helical main chains and a transverse connecting sequence. The transverse connecting sequence connects the two helical main chains into a DNA chain structure. The microrobot main structure has an adjustable total length along the central axis, and the outer envelope diameter gradually increases from both ends to the middle along the axial direction to the maximum diameter, so that the microrobot main structure forms a bipyramidal structure. The microrobot main structure is obtained by 3D printing. The magnetic functional layer is a nickel layer covering the surface of the microrobot main structure, and the biocompatible layer is a titanium layer covering the surface of the magnetic functional layer. The driving method is implemented according to the following steps: Step 1: After being magnetized, the magnetic functional layer forms a fixed magnetization direction and has a preset misalignment angle with the central axis of the microrobot's main structure; Step 2: In the initial state, the direction of the magnetic field is collinear with the magnetization direction of the microrobot, and the relative angle between them is... β When the magnetic torque is zero, the microrobot remains stationary. Step 3: As the magnetic field moves at an angular velocity oh 1. Rotation: The fluid generates viscous drag torque on the microrobot. The magnetization direction of the microrobot lags behind the magnetic field direction. The relative angle between the two... β The magnetic field force is not equal to zero; it gradually increases as the magnetic field rotates, and the magnetic torque also gradually increases accordingly. When the magnetic torque exceeds the viscous drag torque generated by the fluid on the microrobot, the microrobot enters an acceleration state. At this time, the angular velocity of the microrobot is less than the angular velocity of the magnetic field. oh 1; Step 4: With the angular velocity of the magnetic field oh 1 continuously increases, as the angular velocity of the microrobot and the angular velocity of the magnetic field increase... oh 1. Upon synchronization, the magnetic torque and the viscous drag torque generated by the fluid on the microrobot reach dynamic equilibrium, and the microrobot enters a state of uniform synchronous rotation at a constant angular velocity. oh Synchronous motion with the rotating magnetic field, when the magnetic field angular velocity oh1. Continuously increasing the angle between the magnetization direction and the magnetic field direction of the microrobot β When the angle is increased to 90°, the magnetic torque reaches its maximum value, and the microrobot achieves its maximum speed. Step 5: With the angular velocity of the magnetic field oh With a further increase of 1, the relative angle between the magnetization direction and the magnetic field direction of the microrobot... β When the angle is greater than 90°, the magnetic torque decreases. When the magnetic torque is no longer sufficient to overcome the viscous resistance torque of the fluid on the microrobot, the microrobot can no longer maintain synchronous rotation with the rotating magnetic field and enters a state of loss of synchronization. Step 6: When the microrobot enters a confined space, it propels itself in a spiral motion with its right end as the head. By changing the direction of the magnetic field rotation axis, it can propel itself in a spiral motion with its left end as the head. The main structure of the microrobot does not need to perform a complete turnaround, thus achieving a seamless switch between forward and return, and has bidirectional spiral propulsion capability.

[0005] The two helical main chains have the same chirality, which makes the microrobot's main structure form an overall shape with a double helix structure. By pre-setting a phase difference in the circumferential direction through the transverse connection sequence, the two helical main chains can form multiple repeating double helix segments in the axial direction.

[0006] In the main structure of the microrobot, the pitch of each helical segment of the two helical main chains varies linearly in the axial direction. The pitch of the microrobot is... L 1. Lead is L 2. The helix angle is i The number of spiral heads is N The constant relationship is shown in the following equation: (1) (2) (3) This enables the microrobot to have stable propulsion capabilities under the influence of a magnetic field.

[0007] The lateral connection sequence is spaced axially as follows: d 3, and d 3. Pitch of the microrobot L 1 satisfies 0≤ d 3≤0.5 L 1.

[0008] The microrobot's main structure has an adjustable total length. By adjusting the helix angle, the number of helix heads, the cone angle, and the spacing and diameter of the lateral connection sequences, a DNA chain-like magnetic microrobot structure suitable for different working environments can be formed, while satisfying 0° ≤ i ≤90°, 1≤ N ≤5.

[0009] The nickel layer of the magnetic functional layer is formed by magnetron sputtering technology, and the thickness of the magnetic functional layer is... d n It varies with the surface area of ​​the microrobot's main structure. d n = k 1 S m ,in, k 1 represents the thickness coefficient of the nickel layer. S m The surface area of ​​the microrobot's main structure is given by [reference to surface area]. The titanium layer of the biocompatible layer is formed using magnetron sputtering technology, and the thickness of the biocompatible layer is [reference to surface area]. d t It varies with the thickness of the magnetic functional layer. d t = k 2 d n ,in, k 2 represents the thickness coefficient of the titanium layer, which enables the microrobot to have strong driving force and biocompatibility.

[0010] The beneficial effects of this invention are: (1) The biconical DNA chain magnetic microrobot of this invention promotes fluid adhesion and inhibits boundary layer separation through its biconical structure, reducing the influence of fluid resistance and friction, thereby improving the motion speed. In high viscosity or complex fluid environments, the biconical structure design provides a smoother motion trajectory, reduces fluid drag, and extends its continuous operation time in complex environments; (2) The biconical DNA chain magnetic microrobot of this invention adopts a structure of two double-helix main chains and transverse connecting sequences. The chirality and phase difference of the two helices enable the microrobot to provide [certain functions] during rotation. Stable propulsion force, lateral connection sequence provides distance constraint, the structure improves torsional stiffness and geometric symmetry, reduces yaw and attitude fluctuation in rotational propulsion, and improves trajectory stability; (3) The double-cone DNA chain magnetic microrobot of the present invention has bidirectional helical propulsion capability. When moving forward, the right end is used as the head for propulsion. When returning, the direction of the rotation axis of the rotating magnetic field is changed so that the left end is used as the head for helical propulsion. The propulsion direction is switched by the angle of the rotation axis of the rotating magnetic field. The microrobot body does not need to perform the overall turning action, thereby achieving seamless switching between forward and return, improving task execution efficiency and operational flexibility. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the main structure of a biconical DNA chain magnetic microrobot; Figure 2 This is a schematic diagram of the driving principle of a biconical DNA chain magnetic microrobot. Figure 3This is a schematic diagram of the bidirectional propulsion of a biconical DNA chain magnetic microrobot. Figure 4 This is a scanning electron microscope image of a microrobot after 3D printing; Figure 5 This is a comparative schematic diagram of magnetic microrobot structures with cylindrical, conical-cylindrical, and biconical geometric features. Detailed Implementation

[0012] Specific implementation method one: Combining Figure 1 The biconical DNA chain-like magnetic microrobot has a helical chain structure, comprising a main microrobot structure 1-1, a magnetic functional layer 1-2, and a biocompatible layer 1-3. The surface of the main microrobot structure 1-1 is coated with a 2 µm thick nickel layer as the magnetic functional layer 1-2 using magnetic sputtering technology, and then covered with a 200 nm thick titanium layer as the biocompatible layer 1-3. This design endows the main microrobot structure 1-1 with the ability to respond to an external rotating magnetic field, ensuring the biocompatibility of the microrobot in a biomedical environment and avoiding damage to cells or biological tissues. Through pre-magnetization treatment, the magnetic functional layer 1-2 forms a fixed magnetization direction, and this direction has a pre-set misalignment angle with the central axis of the microrobot, enabling the microrobot to generate driving torque and achieve stable propulsion under the action of an external rotating magnetic field. The total axial length of the main microrobot structure 1-1 is... L =3 mm, maximum outer diameter is D =1 mm, the maximum outer diameter is located in the middle of the body and gradually converges axially from the middle to both ends to form a cone tip, the cone angle is . ψ= The microrobot's main structure 1-1 adopts a symmetrical DNA chain framework configuration, consisting of two helical main chains surrounding a central axis at a helical angle of 48°. θ= It is formed by a 36° spiral extension, and the diameter of a single spiral chain is [missing information]. d 2 = 0.14 mm. A transverse connecting sequence 1-4 is installed between the two helical main chains to reinforce and space the helical chains. The wire diameter of the transverse connecting sequence 1-4 is... d 1 = 50 µm, the spacing between lateral connection sequences 1-4 is d 3 = 100 µm, the transverse connecting sequences 1-4 are arranged axially at intervals and perpendicular to the central axis to form a DNA double helix linker structure.

[0013] Specific Implementation Method Two: Combining Figure 2 and Figure 3 Note that in the initial state 2-1, the direction of the applied magnetic field is collinear with the magnetization direction of the microrobot, and the relative angle between them is... β Equal to zero, magnetic torque T q With the magnetic field at zero, the microrobot remains stationary, moving at an angular velocity of zero. oh 1. Rotation causes the fluid to generate viscous drag torque on the microrobot. T r The magnetization direction of the microrobot lags behind the magnetic field direction, and the relative angle between the two is... β Not equal to zero, gradually increasing as the magnetic field rotates, magnetic torque T q The magnetic torque also gradually increases accordingly. T q Greater than the viscous drag torque generated by the fluid on the microrobot T r At this point, the microrobot enters acceleration state 2-2, and the angular velocity of the microrobot is less than the angular velocity of the applied magnetic field. oh 1. With the angular velocity of the magnetic field oh 1 continuously increases, as the magnetic torque T q Viscous drag torque generated by the fluid on the microrobot T r When dynamic equilibrium is reached, the microrobot enters a uniform velocity state 2-3, maintaining a constant angular velocity. oh Moving synchronously with the magnetic field, when the magnetic field angular velocity oh 1. Continuously increasing the angle between the magnetization direction and the magnetic field direction of the microrobot β When the angle is increased to 90°, the magnetic torque T q When the magnetic field angular velocity reaches its maximum value, the microrobot achieves its maximum speed. oh With a further increase of 1, the relative angle between the magnetization direction and the magnetic field direction of the microrobot... β Greater than 90°, magnetic torque T q Consequently, the magnetic torque decreases. T q No longer sufficient to overcome the viscous drag torque of the fluid on the microrobot T r When the microrobot can no longer maintain synchronous rotation with the rotating magnetic field, it enters a state of being out of step. When the microrobot enters a confined space, it can propel itself in a spiral motion with its right end as the head (3-1) and change the direction of the magnetic field rotation axis. It can then propel itself in a spiral motion with its left end as the head (3-2). The main structure of the microrobot does not need to perform an overall turning action, thus achieving a seamless switch between forward and return, and has bidirectional spiral propulsion capability.

[0014] Specific implementation method three: Figure 4The image shows a scanning electron microscope image of the 3D-printed microrobot. The double helix backbone is continuously wound, with the outer diameter increasing in the middle and decreasing at both ends, forming a double-conical envelope outline. In the magnified view, the transverse connecting sequences 1-4 are arranged sequentially along the axis and connected to the two helical backbones respectively, forming a DNA chain framework. The axial spacing between adjacent transverse connecting sequences 1-4 is 50 μm, and the spacing between transverse connecting sequences 1-4 is consistent.

[0015] Specific implementation method four: Combination Figure 5 The microrobot structures, from A to C, represent magnetic microrobots with cylindrical, conical-cylindrical, and biconical geometric features, respectively. Cylindrical geometry is suitable for open fluid spaces with weak boundary effects. Conical-cylindrical geometry is suitable for scenarios with narrow inlet, gradually changing scale, or the need to drill into target areas. The biconical symmetric structure can better balance fluid dynamics and effectively suppress uncontrollable swaying and lateral drift that are prone to occur under low-frequency drive. The conical end helps reduce fluid resistance and optimize the flow field distribution, thereby achieving higher propulsion speed under the same magnetic field parameters. The biconical design gives it more consistent performance in both forward and reverse motion, making it suitable for complex environments with high viscosity, strong disturbances, narrow channels, and near-wall motion, or for mission scenarios that require frequent back-and-forth movement without the desire to turn around.

Claims

1. A method for driving a biconical DNA strand-like magnetic microrobot structure, characterized in that: The magnetic microrobot structure includes a microrobot main structure (1-1), a magnetic functional layer (1-2), and a biocompatible layer (1-3). The microrobot main structure (1-1) includes two helical main chains and a transverse connecting sequence (1-4). The transverse connecting sequence (1-4) connects the two helical main chains into a DNA chain structure. The microrobot main structure (1-1) has an adjustable total length along the central axis, and the outer envelope diameter gradually increases from both ends to the middle along the axial direction to the maximum diameter, so that the microrobot main structure (1-1) forms a bipyramidal structure. The microrobot main structure (1-1) is obtained by 3D printing. The magnetic functional layer (1-2) is a nickel layer covering the surface of the microrobot main structure (1-1), and the biocompatible layer (1-3) is a titanium layer covering the surface of the magnetic functional layer (1-2). The driving method is implemented according to the following steps: Step 1: After being magnetized, the magnetic functional layer (1-2) forms a fixed magnetization direction and has a preset misalignment angle with the central axis of the microrobot main body structure (1-1); Step 2: In the initial state (2-1), the direction of the magnetic field is collinear with the magnetization direction of the microrobot, and the relative angle between them is... β When the magnetic torque is zero, the microrobot remains stationary. Step 3: As the magnetic field moves at an angular velocity ω 1. Rotation: The fluid generates viscous drag torque on the microrobot. The magnetization direction of the microrobot lags behind the magnetic field direction. The relative angle between the two... β The magnetic torque is not equal to zero and gradually increases as the magnetic field rotates. When the magnetic torque is greater than the viscous drag torque generated by the fluid on the microrobot, the microrobot enters an acceleration state (2-2). At this time, the angular velocity of the microrobot is less than the angular velocity of the magnetic field. ω 1; Step 4: With the angular velocity of the magnetic field ω 1 continuously increases, as the angular velocity of the microrobot and the angular velocity of the magnetic field increase... ω 1. Upon synchronization, the magnetic torque and the viscous drag torque generated by the fluid on the microrobot reach dynamic equilibrium, and the microrobot enters a state of uniform synchronous rotation (2-3), maintaining a constant angular velocity. ω Synchronous motion with the rotating magnetic field, when the magnetic field angular velocity ω 1. Continuously increasing the angle between the magnetization direction and the magnetic field direction of the microrobot β When the angle is increased to 90°, the magnetic torque reaches its maximum value, and the microrobot achieves its maximum speed. Step 5: With the angular velocity of the magnetic field ω With a further increase of 1, the relative angle between the magnetization direction and the magnetic field direction of the microrobot... β When the angle is greater than 90°, the magnetic torque decreases. When the magnetic torque is no longer sufficient to overcome the viscous resistance torque of the fluid on the microrobot, the microrobot can no longer maintain synchronous rotation with the rotating magnetic field and enters a state of loss of synchronization. Step 6: When the microrobot enters a confined space, it propels itself in a spiral motion with its right end as the head (3-1). By changing the direction of the magnetic field rotation axis, it can propel itself in a spiral motion with its left end as the head (3-2). The main structure of the microrobot (1-1) does not need to perform a complete turning action, thus achieving a seamless switch between forward and return, and has bidirectional spiral propulsion capability.

2. The biconical DNA chain-like magnetic microrobot structure according to claim 1, characterized in that: The two helical main chains have the same chirality, which makes the microrobot main structure (1-1) form an overall shape with a double helix structure. By pre-setting a phase difference in the circumferential direction through the transverse connection sequence (1-4), the two helical main chains can form multiple repeating double helix segments in the axial direction.

3. The biconical DNA chain-like magnetic microrobot structure according to claim 1, characterized in that: In the main structure (1-1) of the microrobot, the pitch of each helical segment of the two helical main chains varies linearly in the axial direction. The pitch of the microrobot is... L 1. Lead is L 2. The helix angle is θ The number of spiral heads is N The constant relationship is shown in the following equation: （1） （2） （3） This enables the microrobot to have stable propulsion capabilities under the influence of a magnetic field.

4. The biconical DNA chain-like magnetic microrobot structure according to claim 1, characterized in that: The lateral connection sequences (1-4) are spaced axially as follows: d 3, and d 3. Pitch of the microrobot L 1 satisfies 0≤ d 3≤0.5 L 1.

5. The biconical DNA chain-like magnetic microrobot structure according to claim 1, characterized in that: The main structure of the microrobot (1-1) has an adjustable total length. By adjusting the helix angle, the number of helix heads, the cone angle, and the spacing and diameter of the transverse connecting sequences (1-4), a DNA chain-like magnetic microrobot structure suitable for different working environments can be formed, and the following condition is met: 0°≤ θ ≤90°, 1≤ N ≤5.

6. The biconical DNA chain-like magnetic microrobot structure according to claim 1, characterized in that: The nickel layer of the magnetic functional layer (1-2) is formed by magnetron sputtering technology, and the thickness of the magnetic functional layer (1-2) is... d n The surface area of ​​the main structure (1-1) of the microrobot varies, and there is d n = k 1 S m ,in, k 1 represents the thickness coefficient of the nickel layer. S m The surface area of ​​the main structure (1-1) of the microrobot is given. The titanium layer of the biocompatible layer (1-3) is formed by magnetron sputtering technology. The thickness of the biocompatible layer (1-3) is given. d t The thickness varies with the magnetic functional layer (1-2). d t = k 2 d n ,in, k 2 represents the thickness coefficient of the titanium layer, which enables the microrobot to have strong driving force and biocompatibility.

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