Magnetic motion rigid-flexible combined micro-nano robot and preparation method thereof

Abstract

The application provides a magnetic control motion rigid-flexible combined micro-nano robot and a preparation method thereof, and adopts a laser direct writing secondary printing technology to realize high-precision integration of rigid-flexible structures in micro-nano scales and solve the contradiction between motion performance and environmental adaptability. A removable protective top cover structure is adopted to solve the problem of unexpected magnetization of flexible parts and ensure the deformation characteristics of the flexible structure and the magnetic control motion of the rigid-flexible combined structure. In combination with the laser direct writing printing and the magnetic control sputtering technology, various complex three-dimensional structures can be processed, and the manufacturing process is simplified. The prepared robot has a wide prospect in the biomedical field, especially in the precise medical field such as targeted drug delivery and minimally invasive surgery, and is expected to bring breakthroughs in diagnosis and treatment technologies. Meanwhile, the preparation process reduces the cost of traditional micro-nano processing and improves the production efficiency, provides a feasible path for technology transformation, and solves the problem that single-material micro-nano robots cannot simultaneously have high motion performance and high environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of micro-nano robot technology, and more specifically, to a magnetically controlled rigid-flexible micro-nano robot and its fabrication method. Background Technology

[0002] Micro- and nanorobot technology, with its controllable motion capabilities at a tiny scale, has shown great application potential in targeted drug delivery, minimally invasive surgery, environmental remediation, and micro / nano manufacturing. Among these, magnetically controlled actuation is considered one of the most promising actuation strategies for biomedical applications due to its advantages such as non-contact operation, good biocompatibility, strong penetration, and high controllability.

[0003] Currently, micro- and nanorobots are mainly classified into rigid and flexible types based on their structure. Rigid micro- and nanorobots are fabricated using materials that are unresponsive to environmental stimuli. The most representative rigid structure is the helical robot. For example, Totori et al. used the negative photoresist IP-L to fabricate a rigid helical robot with a length of 8.8 μm, achieving a high-efficiency motion of 2.5 BL / s under the control of a rotating magnetic field. Huang et al. used the negative photoresist SU-8 to fabricate a rigid helical robot with a length of 20 μm, achieving a high-efficiency motion of nearly 60 μm / s, or 3 BL / s, under the control of a rotating magnetic field. The motion control of rigid micro- and nanorobots is simple and their motion efficiency is relatively high. Magnetism can be imparted to micro- and nanorobots by plating magnets onto the rigid structure, thereby enabling controllable and efficient motion under magnetic field control. However, because rigid materials are inherently hard and lack stimulus responsiveness, they cannot deform and have poor adaptability to complex environments.

[0004] Flexible micro- and nanorobots are fabricated using soft materials that respond to environmental stimuli. They can deform under external environmental stimuli to adapt to complex environments. For example, Jin et al. designed a double-layer beam structure with different cross-linking densities using pH-responsive hydrogels. This structure achieves bending deformation by utilizing the different water absorption and loss properties under pH stimulation. Based on this double-layer beam structure, they designed deformable micro-scaffolds and micro-umbrellas. While flexible micro- and nanorobots are easily deformable, their motion capabilities are poor and their efficiency is low. This limitation in material properties greatly restricts their application in complex environments. Therefore, developing a rigid-flexible micro- and nanorobot that can balance efficient motion and large deformation, along with a reliable fabrication method, has become a key technical problem urgently needing to be solved in this field. Therefore, this paper proposes a magnetically controlled rigid-flexible micro- and nanorobot and its fabrication method. Summary of the Invention

[0005] The purpose of this invention is to provide a magnetically controlled, rigid-flexible combined micro / nano robot and its preparation method, in order to solve the technical problem that existing single-material micro / nano robots cannot simultaneously achieve high mobility and high environmental adaptability.

[0006] To achieve the above-mentioned objectives, this invention provides the following technical solution: a method for fabricating a magnetically controlled, rigid-flexible hybrid micro / nano robot, comprising the following steps: Step 1: Fabrication of the rigid structure: A rigid photoresist, such as SU-8 or IP-L780, is coated (dispensed) onto the substrate. Two-photon polymerization is used to scan and cure the photoresist according to the designed rigid structure. Uncured photoresist layers are then removed by development to obtain a high-precision rigid structure. High-precision alignment marks can be designed at both ends of the rigid structure during the design process. Step 2, Fabrication of the flexible structure: The hydrogel precursor is dropped onto the surface of the rigid micro / nano structure printed in Step 1. The alignment marks are identified using a microscope vision system, and a precise coordinate system is established to calibrate the precision motion platform. After calibration, the solidified hydrogel precursor is scanned along the preset flexible structure path using a secondary laser scan. Uncured parts are then rinsed away to obtain a flexible structure combined with the rigid structure. Step 3, Local protective treatment of the flexible structure: In order to prevent the flexible structure from becoming magnetized and hardened by the subsequent magnetization process, a removable three-dimensional rigid protective cover is designed. Its dimensions in both the horizontal and vertical directions are larger than the flexible joint below it, and it completely covers the flexible structure, thereby providing all-round protection for the flexible joint during the magnetization process.

[0007] Step 4: Imparting and post-processing the magnetron sputtering function: Using magnetron sputtering technology, directional magnetic atoms are deposited on the rigid structure from top to bottom. After sputtering, the three-dimensional rigid protective cap described in Step 3 is removed, exposing the unmagnetized flexible structure below, which retains its original characteristics. The final result is a magnetron-controlled rigid-flexible micro / nano robot with a strong magnetic response in the rigid part and large deformation in the flexible part.

[0008] As a preferred embodiment of the present invention, the protective top cover in step 3 can also be printed from a soluble material. After the magnetic plating is completed, the entire sample is immersed in a solvent to dissolve the top cover, thereby exposing the flexible structure and enabling mass production post-processing. Furthermore, the deposition of the magnetic thin film can also be accomplished using electron beam evaporation or electrochemical deposition.

[0009] As a preferred embodiment of the present invention, the rigid structure is made of photoresist, and the flexible structure is made of environmentally responsive hydrogel.

[0010] As a preferred technical solution of the present invention, in the rigid-flexible combination structure, the flexible part is provided with a rigid top cover in the horizontal and vertical directions, which can realize the magnetization of the rigid parts of the rigid-flexible combination robot and maintain the deformability of the flexible joint parts.

[0011] As a preferred technical solution of the present invention, in step 4, the magnetic film is a nickel thin film, which is directionally deposited on the surface of a rigid structure by magnetron sputtering technology.

[0012] As a preferred technical solution of the present invention, the rigid-flexible combined structure involves symmetrical structural variant design and asymmetrical structural variant design.

[0013] A magnetically controlled rigid-flexible micro / nano robot includes a rigid structure, a flexible structure, and a magnetic layer. The robot has an integrated rigid-flexible structure, the surface of which is covered with a magnetic thin film, and the flexible structure is essentially non-magnetic.

[0014] As a preferred embodiment of the present invention, the rigid structure is made of photoresist, and the flexible structure is made of environmentally responsive hydrogel.

[0015] As a preferred embodiment of the present invention, the magnetic layer is a nickel thin film with a thickness of 100-200 nm.

[0016] As a preferred technical solution of the present invention, the flexible structure is seamlessly connected to the rigid structure, the magnetic layer is deposited only on the surface of the rigid structure, and high-precision alignment marks are provided at both ends of the rigid structure.

[0017] As a preferred technical solution of the present invention, the rigid-flexible combined structure adopts a symmetrical structure or an asymmetrical structure.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention achieves high-precision integration of rigid and flexible structures at the micro-nano scale through laser direct writing secondary printing technology, enabling the robot to simultaneously possess high magnetic responsiveness, mobility and excellent environmental adaptability, effectively solving the contradiction between mobility performance and environmental adaptability.

[0019] (2) The present invention innovatively adopts a removable protective top cover structure, which successfully solves the technical problem of unintended magnetization of the flexible part. The rigid structure has a high magnetic element content while the flexible structure has a low magnetic element content, which ensures that the flexible structure maintains excellent deformation characteristics and can realize the magnetic control motion of the rigid-flexible combination structure.

[0020] (3) The present invention uses a combination of laser direct writing printing and magnetron sputtering to realize the processing of a variety of complex three-dimensional structures without the need for complex masking processes, which greatly simplifies the manufacturing process and provides an efficient platform for customizing functional micro-nano robots with excellent deformation and motion performance for different application scenarios.

[0021] (4) The rigid-flexible micro-nano robots prepared by this invention show broad application prospects in the biomedical field, especially in precision medicine fields such as targeted drug delivery and minimally invasive surgery, which are expected to bring new breakthroughs in diagnostic and treatment technologies. At the same time, the preparation process effectively reduces the cost of traditional micro-nano processing, providing a feasible path for improving production efficiency and promoting technology transformation. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the magnetically controlled rigid-flexible micro / nano robot provided by the present invention. Figure (a) shows the design of the rigid structure top cover of the rigid-flexible micro / nano robot; (b) shows the rigid-flexible coupled micro / nano robot after magnetization. This visually demonstrates the core components of the invention and its final product. Figure 2 A schematic diagram illustrating the deformability of the magnetically controlled rigid-flexible robot provided by this invention; This diagram illustrates how a top cover protects the flexible structural components, which are not magnetically coated. Upon exposure to external pH stimuli, the overall structure contracts from a bent state to a circular shape before stretching back to a planar state. Scale bar: 100μm Figure 3 A schematic diagram illustrating the motion of the magnetically controlled rigid-flexible robot provided by this invention; This figure illustrates a rigid-flexible micro / nano robot that can move controllably to the right under a uniform rotating magnetic field, achieving a speed of 670 μm / s, or 2.6 times its body length per second, demonstrating highly efficient motion performance. Scale bar: 100 μm; Figure 4 Deformation and motion diagrams of the magnetically controlled rigid-flexible robot provided by this invention; This figure illustrates the controllable deformation and movement of a magnetically controlled rigid-flexible micro / nanorobot under pH stimulation and a uniform rotating magnetic field. (a) Deformation of the robot after magnetization in an acidic environment; (b) Magnetically controlled movement of the robot in an alkaline environment; (c) Magnetically controlled movement of the robot in an acidic environment. Scale bar: 100 μm Figure 5 This is a schematic diagram illustrating the motion performance of the magnetically controlled rigid-flexible robot provided by the present invention before and after structural transformation. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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 specific implementations of the present invention and are not limited to all embodiments.

[0024] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely illustrates some embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] It should be noted that, in the absence of conflict, the embodiments and features and technical solutions in the embodiments of the present invention can be combined with each other. It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0026] Example 1: A method for fabricating a magnetically controlled, rigid-flexible hybrid micro / nano robot, comprising the following steps: Step 1, Substrate preparation: Ultrasonically clean the glass substrate with isopropyl alcohol (IPA), then rinse with deionized water and dry with a nitrogen gun; Step 2, rigid adhesive dispensing: Use a pipette to take 100 μL of IPL-780 photoresist and slowly drop it into the center of a 15 mm × 15 mm glass sample; Step 3, Rigid Structure Printing: A glass substrate coated with IPL-780 photoresist is placed into a Nanoscribe Photonic Professional GT 3D laser direct writing system, and 3D printing is performed using a 780 nm wavelength laser. The printing process employs Galvo scanning writing mode (30 mW power, 100 μm / s scanning speed), which allows for efficient and high-precision sample preparation. Step 4, Development: After printing, place the sample in an isopropanol solution for development for 60 seconds. Step 5, Flexible Adhesive Dispensing: Using a pipette, draw 100 μL from the reagent bottle containing the pH-responsive hydrogel precursor and dispense it onto the glass substrate developed in Step 3. The pH-responsive hydrogel precursor consists of 20 wt% acrylic monomer, 5 wt% dipentaerythritol pentaacrylate crosslinking agent, triethanolamine (TEOA) photosensitizer, 4,4'-bis(diethylamino)benzophenone (EMK) and N,N-dimethylformamide (DMF) photoinitiators, and polyvinylpyrrolidone intensity modifier. Step 6, Alignment: Place the sample after dispensing into the Nanoscribe Photonic Professional GT 3D laser direct writing system. High-precision alignment marks are designed at both ends of the rigid structure. The marks are identified and a coordinate system is established through the microscope vision system. The instrument motion platform is calibrated so that the printing start point during the second printing is precisely matched with the mark coordinates. Step 7, Flexible Structure Printing: The designed structure is 3D printed using a 780 nm wavelength laser and Galvo scanning writing method (laser power 20mW, scanning speed 100μm / s), and the hydrogel precursor is scanned and solidified according to the preset flexible structure path. Step 8, Development: After printing, place the sample in an isopropanol solution for development for 60 seconds to form a flexible part that is seamlessly integrated with the rigid structure. Then rinse with deionized water and dry with nitrogen. Step 9: Second dispensing of rigid adhesive. Use a pipette to take 150 μL of IPL-780 photoresist and slowly drop it into the center of the glass sample printed with rigid-flexible micro / nano robots; Step 10, Secondary Alignment: Identify alignment marks and establish a coordinate system through the microscope vision system, calibrate the instrument motion platform, and ensure that the printing start point during the secondary printing is precisely matched with the mark coordinates; Step 11: Printing the Flexible Structure Protective Top Cover: Design a rigid protective top cover above all flexible structures (the top cover should be 20μm vertically and 15μm horizontally away from the flexible structure it protects). Place a glass substrate coated with IPL-780 photoresist into a Nanoscribe Photonic Professional GT 3D laser direct writing system and perform 3D printing using a 780nm wavelength laser. The printing process uses Galvo scanning writing mode (30 mW power, 100μm / s scanning speed). Step 12, Magnetization: A 150 nm thick Ni film was deposited on the developed sample using a Q150TS instrument via DC magnetron sputtering. During the sputtering process, the sample stage rotated at 70 rpm to ensure the micro / nanorobot was magnetized as uniformly as possible. Simultaneously, the sample stage was kept at a 0° tilt angle, allowing the parts of the micro / nanorobot without the three-dimensional protective cap to be sputtered with magnetic material, while the parts with the three-dimensional protective cap remained unsputtered, thus endowing the rigid-flexible micro / nanorobot with magnetron-controlled motion characteristics. Step 13: Removal of the flexible protective top cover: Place the sample after magnetization in the probe station, use a 10μm probe to pick off and remove the flexible protective top cover from the substrate, and then peel the magnetized rigid-flexible micro-nano robot off the substrate to obtain a magnetically controlled rigid-flexible micro-nano robot with excellent motion and deformation performance.

[0027] In this invention, laser direct-write printing technology is used to scan and solidify a pre-set rigid structure path, followed by development to remove uncured adhesive layers, resulting in a high-precision rigid structure. High-precision alignment marks are then designed at both ends of the rigid structure. A microscope vision system is used to identify these alignment marks and establish a precise coordinate system to calibrate the motion platform. After calibration, a second laser scan is performed to solidify the hydrogel precursor along a pre-set flexible structure path, followed by rinsing to remove uncured portions, resulting in a flexible structure integrated with the rigid structure. To prevent the flexible structure from hardening due to magnetization during subsequent magnetization processes, a removable rigid protective cap is designed, with dimensions larger than the flexible joint below it in both horizontal and vertical directions, completely covering it. Magnetron sputtering technology is used to deposit directional magnetic atoms onto the rigid structure from top to bottom. After sputtering, the rigid protective cap is removed, ultimately yielding a magnetically controlled rigid-flexible micro / nano robot with a strong magnetic response to the rigid structure and high adaptability to the flexible structure.

[0028] The rigid structure is made of photoresist, while the flexible structure is made of environmentally responsive hydrogel. In this rigid-flexible hybrid structure, the flexible portion has rigid caps in both the horizontal and vertical directions, enabling magnetization of the rigid parts of the robot while maintaining the deformability of the flexible joints. The magnetic film is a nickel thin film, directionally deposited on the surface of the rigid structure using magnetron sputtering. The rigid-flexible hybrid structure involves both symmetrical and asymmetrical structures. The robot possesses an integrated rigid-flexible structure, with the rigid structure surface covered by a magnetic film and the flexible structure being essentially non-magnetic, thus achieving a rigid-flexible micro / nano robot that combines efficient motion with large deformation.

[0029] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described herein. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present invention, as well as all technical solutions and improvements that do not depart from the spirit and scope of the invention, are covered within the scope of the claims of the present invention.

Claims

1. A method for fabricating a magnetically controlled, rigid-flexible combined micro / nano robot, characterized in that, Includes the following steps: Step 1: Using laser direct writing printing technology, scan and cure the photoresist along the preset rigid structure path, develop and remove the uncured photoresist layer to obtain a high-precision rigid structure; then design high-precision alignment marks at both ends of the rigid structure. Step 2: Use the microscope vision system to identify the alignment marks and establish a precise coordinate system to calibrate the motion platform; After calibration, the pH-responsive hydrogel precursor is scanned and solidified through a second laser scan along a preset flexible structure path. The uncured part is then rinsed away to obtain a flexible structure that is combined with a rigid structure. Step 3: To prevent the flexible structure from becoming hardened by magnetization during the subsequent magnetization process, a removable rigid protective cover is provided. The rigid protective cover is made of photoresist and its dimensions in both the horizontal and vertical directions are larger than the flexible joint below it, so as to completely cover the flexible joint. Step 4: Using DC magnetron sputtering technology, nickel atoms are directionally deposited on the rigid structure from top to bottom to form a nickel film, thus completing the magnetization of the rigid structure. After sputtering, the rigid protective top cover described in Step 3 is removed, and finally, a magnetron-controlled rigid-flexible micro-nano robot is obtained.

2. The method for fabricating a magnetically controlled, rigid-flexible combined micro / nano robot according to claim 1, characterized in that, The rigid-flexible micro / nano robots are constructed using either symmetrical or asymmetrical structural variants.

3. A magnetically controlled rigid-flexible hybrid micro / nano robot prepared according to any one of claims 1 to 2, characterized in that, The robot comprises a rigid structure, a flexible structure, and a magnetic layer. It has an integrated rigid-flexible structure, with the surface of the rigid structure covered by a nickel magnetic film and the flexible structure being non-magnetic.

4. The magnetically controlled rigid-flexible micro / nano robot according to claim 3, characterized in that, The magnetic layer is a nickel thin film with a thickness of 100-200 nm.

5. A magnetically controlled, rigid-flexible combined micro / nano robot according to claim 4, characterized in that, The flexible structure is seamlessly connected to the rigid structure.

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