Silicon-based light-driven micro-nano robot, preparation method and application thereof

Abstract

The application discloses a silicon-based light-driven micro-nano robot and a preparation method and application thereof, and belongs to the technical field of micro-nano robots. The application first innovatively applies an alpha-Si / metal Schottky junction to the design of a micro-nano robot, replaces the complex process steps in the prior art, and can prepare the silicon-based light-driven micro-nano robot through only two simple processes of alpha-Si deposition and metal deposition, and at the same time, breaks through the bottleneck of single structure and limited function expansion of a traditional micro-nano robot, and successfully realizes the construction of a programmable, universal and expandable micro-nano robot. The design of the light-driven micro-nano robot based on alpha-Si is a structural innovation first realized in the field, and provides a new technical path for the energy supply and function integration of the micro-nano robot.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano robotics technology, and in particular relates to a silicon-based optically driven micro-nano robot, its fabrication method, and its application. Background Technology

[0002] Micro- and nano-robots are functional devices capable of controlled motion at the micro- and nano-scale. Their core characteristic lies in their ability to convert external energy sources such as chemical, light, acoustic, or magnetic energy into mechanical energy, thereby performing directional motion and specific tasks in fluid environments. With their precise manipulation capabilities at the microscale, they have demonstrated irreplaceable application value in fields such as micro- and nano-fabrication, environmental remediation, and biomedicine, providing revolutionary solutions to overcome the operational limitations of traditional technologies.

[0003] Among the various driving methods for micro- and nano-robots, optical driving systems have become a hot research topic due to their advantages such as remote non-contact control, fast response speed, and high spatiotemporal resolution. Silicon-based materials, with their excellent photoelectric conversion efficiency, mature semiconductor processing technology, and inherent biocompatibility, are gradually developing into ideal candidate materials for optically driven micro- and nano-robots.

[0004] However, the fabrication technology of light-driven micro / nano robots still faces key bottlenecks: On the one hand, existing methods have limited customization capabilities for geometric structures and low degrees of freedom in control, mostly limited to the fabrication of simple and regular configurations such as spheres and rods, making it difficult to accurately match the diverse and complex customized needs of different application scenarios; on the other hand, current fabrication processes lack universality and economy. The driving cores of existing light-driven micro / nano robots mostly adopt PN junctions or metal-insulator-semiconductor (MIS) structures. These structures require complex processes such as multiple ion implantations, high-temperature annealing, or insulating layer deposition, which are not only cumbersome and technically challenging but also result in high costs for large-scale production. Furthermore, it is difficult to achieve precise construction of cross-dimensional structures within a unified technical framework. These problems further exacerbate the difficulty of practical application transformation of light-driven micro / nano robots and have become the core challenge restricting their further development. Therefore, it is necessary to design a silicon-based light-driven micro / nano robot that combines structural customization flexibility, process universality, and large-scale fabrication potential. Summary of the Invention

[0005] To address the aforementioned technical challenges, this invention proposes a silicon-based optically driven micro / nano robot, its fabrication method, and its applications. This invention innovatively achieves integrated optically driven micro / nano robots based on α-Si / metal Schottky junctions. This technology differs from the complex PN junction or MIS structures used in existing technologies. This invention directly utilizes the α-Si / metal Schottky junction as the driving core, leveraging its naturally built-in electric field to efficiently separate photogenerated electron-hole pairs, generating the required photovoltage for driving. Simultaneously, it significantly simplifies the fabrication process, reducing process difficulty and cost. This technical solution combines ease of operation with process scalability, not only significantly optimizing the dynamic performance of micro / nano robots but also enabling optically controlled orientation, providing a novel technical path for complex scene operation and expanding application boundaries.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for fabricating a silicon-based optically driven micro / nano robot, comprising the following steps: firstly, depositing an α-Si (amorphous silicon) thin film on the surface of a substrate material, and then preparing a metal layer on the α-Si thin film by magnetron sputtering to obtain the silicon-based optically driven micro / nano robot.

[0008] Furthermore, the matrix material is selected from zero-dimensional materials, one-dimensional materials, two-dimensional materials, or three-dimensional materials.

[0009] The materials used in this invention to construct the silicon-based light-driven micro / nano robot substrate encompass any type of material from zero-dimensional to three-dimensional (0D to 3D), offering a wide range of material selection and strong compatibility. The substrate structure of the silicon-based light-driven micro / nano robot described in this invention can be flexibly designed as a random structure within the 0D to 3D dimensional range, exhibiting excellent flexibility and scenario adaptability. Specific structural forms may include, but are not limited to: zero-dimensional micro / nanoparticle structures, one-dimensional micro / nanowire structures, two-dimensional micro-crab-shaped structures, two-dimensional geometrically asymmetric structures, two-dimensional multi-rotationally symmetric structures, and three-dimensional nanotree structures, three-dimensional spiral structures, etc. Therefore, the substrate structure of the light-driven micro / nano robot has no design limitations and can be customized in any shape and structure according to specific application requirements, thereby achieving structural adaptation of the light-driven micro / nano robot for different application scenarios.

[0010] The above design not only significantly optimizes the structural flexibility and driving performance of silicon-based optically driven micro-nano robots, but also lays the foundation for them to achieve precise operation and expand diversified applications in complex scenarios.

[0011] Furthermore, the deposition process of the α-Si thin film is PECVD (Plasma Enhanced Chemical Vapor Deposition). Specific steps include: first, substrate pretreatment, sequentially ultrasonically cleaning with acetone, ethanol, and deionized water for 15 minutes each, followed by nitrogen drying to remove surface impurities and oxide layers; then, selecting zero-dimensional to three-dimensional materials as the substrate for α-Si deposition, using silane and argon as the reaction gases at a flow rate of 300–1000 sccm, operating at a frequency of 13.56 MHz, a process pressure of 0.5–5 Torr, and a deposition rate of 40–60 nm·min. -1 Under these conditions, α-Si thin film deposition is performed to form a light-absorbing layer.

[0012] The α-Si thin film has excellent visible and near-infrared light absorption properties, and can efficiently capture light source energy and generate photogenerated carriers.

[0013] Furthermore, the metal is a metal that matches the band gap of the amorphous silicon thin film.

[0014] Furthermore, the metal is gold or platinum.

[0015] Furthermore, the method for fabricating the silicon-based optically driven micro / nano robot also includes the step of depositing a nickel metal film on the surface of the metal layer.

[0016] Secondly, the present invention also provides a silicon-based optically driven micro / nano robot, which is prepared by the above-described method and has any one of zero-dimensional, one-dimensional, two-dimensional or three-dimensional structures.

[0017] Furthermore, when the silicon-based optically driven micro / nano robot comprises an amorphous silicon thin film and a metal layer, the thickness of the amorphous silicon thin film is 240 nm, and the thickness of the metal layer is 10 nm.

[0018] When the silicon-based optically driven micro / nano robot comprises an amorphous silicon thin film, a metal layer, and a nickel metal film, the thickness of the amorphous silicon thin film is 240 nm, the thickness of the metal layer is 10 nm, and the thickness of the nickel metal film is 20 nm.

[0019] The silicon-based optically driven micro / nano robot prepared in this invention uses an α-Si / Au (or α-Si / Pt) Schottky junction as the driving core.

[0020] The key design of the silicon-based light-driven micro / nano robot provided by this invention lies in building the driving structure using an α-Si / Au (or α-Si / Pt) Schottky structure. This design, on the one hand, endows the robot with highly flexible structural customization capabilities, allowing for the design and fabrication of various 0D to 3D configurations according to requirements; on the other hand, this semiconductor-metal structure can efficiently complete the conversion of photoelectrochemical reaction into mechanical energy, adapting to the driving requirements of various light sources such as visible light and even near-infrared light. Au / Pt has excellent electrocatalytic performance, and can achieve stable and efficient light-driven motion through a self-diffusion migration mechanism induced by photoelectrochemical reaction. In addition, the shadow effect generated by directional light irradiation can be used to precisely control the movement direction of the micro / nano robot. Taking a 3D silicon-based light-driven micro / nano robot as an example, its three-dimensional configuration (such as a three-dimensional nanotree structure) forms an ion concentration difference between the "illuminated area" and the "shadow area" on the robot surface under directional light irradiation, thereby forming a directional driving torque, causing the robot to turn along the light direction, achieving precise control of the light-controlled direction.

[0021] Thirdly, the present invention provides an application of the above-mentioned silicon-based light-driven micro-nano robots in the preparation of products for capturing bacteria, neural modulation, and drug delivery.

[0022] Because the substrate design of the silicon-based light-driven micro / nano robots of this invention is highly flexible and not limited by dimensionality, they can be customized for different application scenarios. Simultaneously, α-Si / Au (or α-Si / Pt) is non-biotoxic and exhibits excellent biocompatibility, making it suitable for long-term in vivo applications and avoiding foreign body reactions or toxicity risks. Specifically, in bacterial capture applications, 0D silicon-based light-driven micro / nano robots, after phage functionalization modification, have demonstrated highly efficient capture capabilities for target bacteria. Combining this functionalization strategy with the advantages of structural customization, its application can be extended to 1D, 2D, and other dimensional micro / nano robots, achieving equally effective bacterial capture. In summary, the design of the silicon-based light-driven micro / nano robots of this invention can be flexibly customized according to specific application needs, thereby adapting to different functional requirements.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] This invention innovatively applies α-Si / metal Schottky junctions to micro-nano robot design for the first time, replacing the complex process steps in existing technologies. Silicon-based light-driven micro-nano robots can be fabricated with only two simple processes: α-Si deposition and metal deposition. At the same time, it breaks through the bottleneck of traditional micro-nano robots with single structure and limited functional expansion, and successfully realizes the construction of programmable, universal, and scalable micro-nano robots. This α-Si-based light-driven micro-nano robot design is a structural innovation achieved for the first time in this field, providing a brand-new technical path for the energy supply and functional integration of micro-nano robots.

[0025] The driving energy of the silicon-based photo-driven micro / nano robot prepared by this invention originates from the photoelectric conversion process of the α-Si / metal Schottky junction under light illumination. It achieves autonomous propulsion through a self-diffusion migration mechanism induced by photoelectrochemical reaction. Compared with traditional chemical driving or single photothermal driving methods, it has advantages such as high energy conversion efficiency and strong driving controllability.

[0026] The silicon-based light-driven micro-nano robot prepared by this invention can be effectively driven in both visible and near-infrared light bands, breaking through the limitation of some light-driven micro-nano robots that only respond to a single spectral range. More importantly, it can achieve precise control of the direction of motion through the directional light shadow effect, and can be adapted to various application scenarios such as near-infrared light driving in deep biological tissues and precise control under visible light, significantly improving the practicality and adaptability of the technology. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a fabrication path diagram of the 0D silicon-based optically driven micro / nano robot in Example 1;

[0029] Figure 2 Image A is a scanning electron microscope image of the 0D silicon-based optically driven micro / nano robot of Example 1, and image B is a thickness measurement image of its α-Si thin film.

[0030] Figure 3 The images shown are scanning electron microscope (SEM) images of 1D-3D silicon-based optically driven micro / nano robots prepared in Examples 2-4. Specifically, A is an SEM image of the 1D silicon-based optically driven micro / nano robot prepared in Example 2, B is an SEM image of the 2D silicon-based optically driven micro / nano robot (two-dimensional micron-shaped crab structure) prepared in Example 3, C is an SEM image of the 2D silicon-based optically driven micro / nano robot (two-dimensional multi-rotational symmetry structure) prepared in Example 3, and D is an SEM image of the 3D silicon-based optically driven micro / nano robot (three-dimensional nanotree structure) prepared in Example 4.

[0031] Figure 4 The diagram shows the motion mechanism of the silicon-based optically driven micro / nano robots prepared in Examples 1-4 under illumination.

[0032] Figure 5The images show the motion of the 0D silicon-based optically driven micro / nano robot prepared in Example 1 under visible and near-infrared light. In the image, A is the migration speed of the 0D silicon-based optically driven micro / nano robot under chopper light irradiation, and B is the speed of the 0D silicon-based optically driven micro / nano robot as the light intensity changes.

[0033] Figure 6 The image shows the navigation trajectory of the 0D silicon-based optically driven micro / nano robot prepared in Example 5 under an external magnetic field.

[0034] Figure 7 This is a schematic diagram of the fabrication process of the 2D silicon-based optically driven micro / nano robot in Example 3;

[0035] Figure 8 This is a diagram illustrating the turning process of the 3D silicon-based optically driven micro / nano robot under directional light in Example 4.

[0036] Figure 9 The motion trajectory diagram of the 0D silicon-based light-driven micro / nano robot capturing bacteria prepared in Example 1;

[0037] Figure 10 In Figure A, the trajectory of bacteria captured by the 1D silicon-based light-driven micro-nano robot prepared in Example 2 is shown, and in Figure B, the trajectory of bacteria captured by the 2D silicon-based light-driven micro-nano robot prepared in Example 3 is shown. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] This invention discloses a method for fabricating a silicon-based optically driven micro / nano robot. The silicon-based optically driven micro / nano robot is constructed based on an α-Si / metal Schottky structure and has diverse customizable structures in the range of 0D to 3D. The fabrication process of silicon-based photo-driven micro / nano robots is as follows: First, substrate selection and pretreatment are performed. An inert material is selected as the substrate, and the substrate dimension is 0D, 1D, 2D, or 3D. The substrate is cleaned to remove surface impurities and oxide layers, resulting in a clean substrate. Next, an amorphous silicon layer is deposited using PECVD technology to deposit an α-Si thin film with a thickness of 240 nm on the surface of the pretreated clean substrate. Subsequently, metal deposition is performed using magnetron sputtering to deposit Au or Pt on the surface of the amorphous silicon layer. The Au / Pt thickness is 10 nm. The α-Si thin film and the Au / Pt layer contact to form a Schottky junction, constituting an α-Si / metal Schottky structure. Finally, separation and collection are performed using ultrasonic treatment to separate the α-Si / metal composite structure from the substrate, obtaining the silicon-based photo-driven micro / nano robot. The separated micro / nano robot is then transferred to a solution for later use. The silicon-based light-driven micro / nano robot of this invention employs a geometrically programmable method. While ensuring efficient light actuation, the introduction of magnetic metal elements allows for precise control of its motion direction via an external magnetic field. Furthermore, the motion direction of the 3D silicon-based light-driven micro / nano robot can be controlled through directional lighting and shadow effects. In addition, embodiments of this invention provide a method for constructing rotating micro-rotor robots by designing structures with multiple rotational symmetries, offering new possibilities for the advancement of micro / nano robot technology. These characteristics make it exhibit excellent application potential in multiple fields, such as bacterial capture, neural modulation, in-situ dynamic monitoring, drug delivery, and micro-area cargo transportation.

[0044] This invention is the first to apply the α-Si / metal Schottky junction optoelectronic structure to the design of micro-nano robots. An amorphous silicon (α-Si) light-absorbing layer is prepared using plasma-enhanced chemical vapor deposition (PECVD), and a Schottky junction is constructed by combining it with gold (Au), overcoming the limitations of traditional driving structures. This method can be customized to construct micro-nano robots with various complex configurations, including 0D, 1D, 2D, and 3D models, offering highly flexible structural design. The fabricated micro-nano robots are driven by self-diffusion electrophoresis induced by photoelectrochemical reactions, achieving efficient propulsion under both visible and near-infrared light. This invention provides a generalized and scalable silicon-based micro-nano robot fabrication scheme, significantly improving the controllability and functional adaptability of light-driven propulsion, and has application value in the fields of biomedicine and environmental monitoring.

[0045] The preparation method of TPM (3-(trimethoxysilane)propyl methacrylate) microspheres in this embodiment of the invention is as follows: In a 250 mL polypropylene beaker, 100 mL of deionized water and 1.2 mL of ammonia water were mixed first, and then 0.5 mL of TPM monomer was slowly added dropwise. The mixture was mechanically stirred at 200 r / min for 1.5 h to form a seed emulsion of 1 μm. Subsequently, TPM monomer (1 mL each time) was added in equal amounts 4-5 times at 1 h intervals. After each addition, the mixture was stirred for 1 h to promote complete hydrolysis-condensation of the monomer and inhibit secondary nucleation. The reaction system was then transferred to a three-necked round-bottom flask for polymerization. 70 mg of azobis(ethylenedioxybutadiene)nitrile was added to the flask, and the mixture was kept at 80 °C for 2 h to complete the polymerization. After centrifugation, the polymerization product was washed multiple times with deionized water to remove unreacted substances. Finally, it was freeze-dried for 24 h to obtain TPM microparticles of approximately 3 μm in size, monodisperse, and with uniform physicochemical properties.

[0046] In this embodiment of the invention, the PECVD deposition process is as follows: an amorphous silicon thin film is deposited using a plasma-enhanced chemical vapor deposition (PECVD) system (OXFORD, PlasmaPro 100 PECVD) with an operating frequency of 13.56 MHz. A mixture of silane (SiH4) and argon (Ar) is used as the process gas, with a constant gas flow rate of 500 sccm, wherein the SiH4:Ar (volume ratio) = 1:19; the deposition process parameters are set as follows: operating frequency 13.56 MHz, process pressure 1 Torr, and deposition rate 50 nm·min. -1 The target film thickness is 240 nm. The deposition substrate material is selected from silicon wafers or quartz glass. These substrates need to undergo strict cleaning treatment before deposition, including cleaning with ethanol, acetone and deionized water, followed by drying with nitrogen to remove moisture, to ensure the cleanliness of the substrate surface, which is crucial for obtaining high-quality films.

[0047] The method for depositing metal by magnetron sputtering in this embodiment of the invention is as follows: A KYKY SBC-12 ion sputtering instrument is used, adapted to metal targets such as gold and platinum. The substrate to be deposited is placed in the center of the sample stage, and the mechanical pump is started to evacuate the vacuum. After the vacuum level drops to 4-6 Pa, the sputtering current is adjusted to 8-10 mA, and the timing is set according to the target film thickness (e.g., 60-300 s for 5-20 nm gold nanoparticles). By fine-tuning the stable current, sputtering is started to complete the metal deposition. The above preparation parameters in the specific embodiment of the invention can be adjusted conventionally as needed.

[0048] The specific operation of patterning using AZ-5214 photoresist through photolithography in this embodiment of the invention is as follows: After cleaning and drying the silicon wafer, HMDS (hexamethyldisilazane) fumigation treatment is performed to enhance the adhesion of the photoresist. Then, AZ-5214 photoresist is dropped onto the center of the substrate, and the spin coating is set to 4000 rpm for 30-40 seconds. After pre-baking at 110°C for 2 minutes, a mask with a pattern size of 2.5×2.5 cm is covered, exposed for 20 seconds, and developed using developer ZX-238 to obtain the desired pattern. The above preparation parameters in the specific embodiment of the invention can be adjusted conventionally as needed.

[0049] The specific operation of oxygen plasma etching in this embodiment of the invention is as follows: the sample to be etched is placed in a plasma cleaner, the oxygen flow rate is set to 10-30 sccm, the processing time is adjusted according to the film thickness (e.g., 200nm PMMA requires 300-400s), the power supply and oxygen are turned off after etching is completed, and the sample is taken out after the chamber is depressurized. The above preparation parameters in the specific embodiment of the invention can be adjusted as needed.

[0050] In this embodiment of the invention, the specific operation of depositing a nickel (Ni) metal film with a thickness of approximately 20 nm on an OD-3D silicon-based light-driven micro / nano robot using an additional thermal evaporation device is as follows: A vacuum resistance thermal evaporation coating device is used, with a Ni target of 99.99% purity installed in a tungsten boat. The OD-3D silicon-based micro / nano robot substrate is placed in the sample stage, and the vacuum system and molecular pump are started. The process continues until the vacuum level reaches 10... -5 After Pa, the current is slowly increased, and the state of the Ni target is observed. When the target begins to melt and a stable evaporation rate is observed (controlled at 0.5-1 Å / s), the current is maintained constant until the film thickness reaches 20 nm. The above preparation parameters in the specific embodiments of the present invention can be adjusted conventionally as needed.

[0051] The standard cleaning process used for pretreatment of N-type silicon wafers in this embodiment of the invention is a conventional technical method and will not be described in detail here.

[0052] The room temperature in this invention refers to 25±2℃.

[0053] Example 1: Fabrication of 0D silicon-based optically driven micro / nano robots

[0054] First, TPM microspheres with a diameter of approximately 3µm were dispersed in anhydrous ethanol to obtain a microsphere dispersion. Then, using a droplet evaporation self-assembly method, an appropriate amount of the microsphere dispersion was dropped onto the surface of a silicon substrate. Utilizing the self-assembly behavior of the microspheres during solvent evaporation, they were tightly arranged on the silicon substrate. Subsequently, the substrate was calcined at 700℃ for 2 hours in an air atmosphere to remove organic components, obtaining a substrate material with a pure SiO2 microsphere array deposited on it. Next, the substrate material was ultrasonically cleaned with acetone, ethanol, and deionized water and dried with nitrogen. First, an amorphous silicon layer of approximately 240nm was deposited using PECVD, and then a 10nm gold layer was deposited using magnetron sputtering to obtain an OD silicon-based optically driven micro / nano robot, which is a micro / nano robot based on a semiconductor / metal structure.

[0055] Figure 1 This is a fabrication path diagram of the OD silicon-based optically driven micro / nano robot in Example 1, where the OD microparticles are SiO2 microspheres. Figure 1 It can intuitively demonstrate the simple preparation process of Schottky junctions.

[0056] Figure 2 Image A is a scanning electron microscope image of the 0D silicon-based photo-driven micro / nano robot of Example 1, and image B is a thickness test image of its α-Si thin film. This image clearly shows the core-shell structure details of the 0D silicon-based photo-driven micro / nano robot and the thickness characteristics of the α-Si thin film, verifying the controllability of the deposition process.

[0057] Example 2: Fabrication of 1D silicon-based optically driven micro / nano robots

[0058] The substrate used in this embodiment is n-type. <100> The specific preparation method for silicon wafers is as follows:

[0059] S1. First, the silicon wafer was ultrasonically cleaned sequentially in deionized water, acetone, and isopropanol for 5 minutes each time, followed by drying with nitrogen. The treated wafer was then immersed in a piranha solution (98% H₂SO₄: 30% H₂O₂ = 3:1 v / v) for 15 minutes to remove organic contaminants from the silicon surface. After thorough rinsing with deionized water, the wafer was further treated with buffered HF (BHF, 5:1) to remove the native oxide layer. AZ-5214 photoresist was used for patterning to create a series of dots (diameter: 1 μm; spacing: 4 μm), followed by wet etching. The silicon wafer was immersed in a solution of 5M HF and 0.02M AgNO₃ for 80 minutes to promote the growth of silicon microwires. Afterward, the silicon microwires were immersed in acetone for 5 minutes and then rinsed with deionized water to remove residual AZ-5214 photoresist. To further purify the silicon microwires, they were immersed in HNO₃ (15M concentration) for 20 minutes to remove residual silver from the surface. To control the morphology, the dense nanowires surrounding the rough silicon wire array were etched away using a 20wt% KOH solution (20 min). Finally, the microwires were thermally oxidized at 1000°C in an oxygen atmosphere for 30 min, resulting in a 100 nm thick SiO2 layer. This SiO2 layer was then etched away using a BHF solution. Subsequently, the silicon wafer was rigorously cleaned sequentially with deionized water and isopropanol, followed by drying to obtain the original one-dimensional silicon nanowires (i.e., the one-dimensional substrate material).

[0060] S2. A 240 nm thick α-Si thin film was deposited on a one-dimensional substrate material using PECVD technology; subsequently, gold nanoparticles with a thickness of approximately 10 nm were deposited on the surface of the above structure using magnetron sputtering. After fabrication, a 1D silicon-based photo-driven micro / nano robot was peeled off from the substrate; this is a micro / nano robot based on a semiconductor / metal structure.

[0061] Example 3 Fabrication of 2D silicon-based optically driven micro / nano robots

[0062] In this embodiment, an N-type silicon wafer pretreated with a standard cleaning process is used as the substrate to ensure that the surface cleanliness meets the requirements of micro-nano processing.

[0063] S1. A SiO2 sacrificial layer is deposited on the surface of a silicon substrate using plasma-enhanced chemical vapor deposition (PECVD) technology, providing a key interface basis for subsequent structural stripping;

[0064] S2. An α-Si functional layer with a thickness of approximately 240 nm was deposited on the SiO2 sacrificial layer using PECVD technology, which served as the core structural material for micro-nano robots;

[0065] S3. To fabricate complex two-dimensional structures, AZ-5214 photoresist was first spin-coated onto the surface of the α-Si functional layer. Then, using a patterned mask customized according to the specific design of the micro-nano robot, the geometric structure conforming to the design specifications was precisely transferred onto the photoresist layer through photolithography exposure and development processes. Using the photoresist pattern as a mask, inductively coupled plasma reactive ion etching (ICP-RIE) dry etching was performed using an SF6 / C4F8 mixed gas. This process achieved anisotropic etching of the α-Si layer, ensuring the perpendicularity of the sidewalls of the two-dimensional structure, and completing a high-fidelity pattern transfer from the photoresist to the α-Si layer.

[0066] S4. After etching, the sample is first immersed in acetone to remove the photoresist. Then, diluted HF (BHF, 5:1) is used to selectively etch the SiO2 sacrificial layer to promote the detachment of the two-dimensional structure from the substrate. Finally, a gold catalyst layer (10nm) is deposited by magnetron sputtering to fabricate a 2D silicon-based photo-driven micro-nano robot.

[0067] Figure 7 This is a schematic diagram of the fabrication process of the 2D silicon-based optically driven micro / nano robot in Example 3, which clearly reflects the continuity and operability of the process steps.

[0068] Example 4: Fabrication of 3D silicon-based optically driven micro / nano robots

[0069] The 3D micro / nano robot in this embodiment is further prepared based on the one-dimensional silicon nanowires (SiNWs) prepared in S1 of Example 2. The specific preparation method is as follows:

[0070] S1. A one-dimensional silicon nanowire substrate was immersed in a mixed solution containing 0.5 mM chloroplatinic acid (H2PtCl6, Sigma-Aldrich) and 0.5 M hydrofluoric acid (HF) for 1.5 min to achieve initial loading of platinum nanoparticles on the SiNWs surface. This loading process was repeated 5 times to ensure the formation of uniformly dispersed small-sized platinum nanoparticles on the one-dimensional silicon nanowire surface. Subsequently, the platinum-loaded silicon substrate was transferred to a vacuum annealing furnace and annealed at 600 °C for 30 min at an argon flow rate of 500 sccm to form a platinum silicide layer, which serves as an ohmic contact between silicon and the subsequently grown TiO2. Next, a 2 wt% polymethyl methacrylate (PMMA) anisole solution was prepared, and a small amount of the solution was dropped onto the SiNWs and placed in a sealed container to allow the solvent to evaporate slowly. Subsequently, part of the PMMA was removed by oxygen plasma etching to precisely expose the SiNWs tips of a predetermined length. The sample was immersed in a dilute HF solution (BHF, 5:1) to remove the native oxide layer on the SiNWs surface, ensuring a clean interface for subsequent processes. A 20 nm thick titanium (Ti) film was sputtered onto the silicon surface using a magnetron sputtering system. The substrate was then annealed for 30 min at 600 °C under vacuum with an argon flow rate of 500 sccm. This annealing step simultaneously transformed the Ti film into a TiO2 seed layer through thermal oxidation and completely removed residual PMMA from the silicon substrate surface through thermal decomposition. Subsequently, 10 mL of deionized water, 10 mL of 37% hydrochloric acid, and 0.28 mL of titanium isopropoxide (TTIP) were mixed. The mixture was stirred continuously for 15 min to ensure homogeneity, and then the SiNWs substrate along with the mixture was transferred to a PTFE-lined stainless steel autoclave. After sealing, the autoclave was placed in a convection oven and reacted at 200 °C for 90 min. This hydrothermal process enabled the growth of TiO2 nanowires on the surface of the TiO2 seed layer, ultimately forming the target three-dimensional nanotree structure.

[0071] S2. A 240 nm thick α-Si thin film was deposited on the three-dimensional nanotree structure using PECVD technology. Then, gold nanoparticles with a thickness of about 10 nm were deposited on the surface of the structure by magnetron sputtering. After the preparation was completed, the 3D silicon-based light-driven micro-nano robot was peeled off from the substrate. It is a micro-nano robot based on an inorganic semiconductor solar cell structure.

[0072] Figure 3The images show scanning electron microscope (SEM) images of 1D to 3D silicon-based optically driven micro / nano robots prepared in Examples 2-4. Specifically, A is the SEM image of the 1D silicon-based optically driven micro / nano robot prepared in Example 2; B is the SEM image of the 2D silicon-based optically driven micro / nano robot (two-dimensional micro-crab-shaped structure) prepared in Example 3; C is the SEM image of the 2D silicon-based optically driven micro / nano robot (two-dimensional multi-rotational symmetry structure) prepared in Example 3; and D is the SEM image of the 3D silicon-based optically driven micro / nano robot (three-dimensional nanotree structure) prepared in Example 4. These images demonstrate that the method for preparing silicon-based optically driven micro / nano robots provided by this invention can successfully prepare 1D silicon nanowires, 2D irregular shapes, and 3D nanotree structures, highlighting the universality of preparing micro / nano robots with different structures based on α-Si / metal Schottky structures.

[0073] Example 5

[0074] Same as Example 1, except that an additional thermal evaporation device is used to deposit a nickel (Ni) metal film with a thickness of about 20 nm on the OD silicon-based light-driven micro-nano robot.

[0075] Example 6

[0076] Same as Example 2, except that an additional thermal evaporation device is used to deposit a nickel (Ni) metal film with a thickness of about 20 nm on the 1D silicon-based light-driven micro-nano robot.

[0077] Example 7

[0078] Similar to Example 3, except that an additional thermal evaporation device is used to deposit a nickel (Ni) metal film with a thickness of about 20 nm on the 2D silicon-based light-driven micro-nano robot.

[0079] Example 8

[0080] Similar to Example 4, except that an additional thermal evaporation device is used to deposit a nickel (Ni) metal film with a thickness of about 20 nm on the 3D silicon-based light-driven micro-nano robot.

[0081] The changes described in Examples 5-8 imply certain advantages of using nickel metal films, particularly in terms of magnetic manipulation. After the fabrication of 0D-3D micro / nano robots, a nickel (Ni) metal film with a thickness of approximately 20 nm is deposited on the micro / nano robots using an additional thermal evaporation device. These micro / nano robots originally achieved self-diffusion migration by locally building an ion concentration gradient through photoelectrochemical reactions; however, the introduction of the magnetic component Ni allows for the control of their migration direction via an external magnetic field. Specifically, precise manipulation of the micro / nano robots can be achieved using an external gradient magnetic field, where the magnetic field strength can range from 0 to 1 T·m. -1The movement direction can be adjusted within a certain range and controlled by a handle, thus enabling the micro-nano robot to migrate along a specific trajectory.

[0082] Test Example 1: Test of Optical Self-Driven Performance and Magnetic Control Performance

[0083] The silicon-based optically driven micro / nano robots prepared in Examples 1-8 were dispersed in a ferrocene methanol solution (70 μM) using ultrasound to obtain suspensions, and the following performance tests were performed:

[0084] Self-driving performance test of light-driven micro / nano robots: First, a suspension containing silicon-based light-driven micro / nano robots prepared in Examples 1-4 was introduced into a sealed chamber assembled from a glass slide and a PDMS container. The autonomous motion behavior of the silicon-based light-driven micro / nano robots under light irradiation was observed using a microscope imaging system, and the motion trajectory, speed, and behavior patterns were recorded.

[0085] Figure 4 The diagram shows the motion mechanism of the silicon-based light-driven micro / nano robots prepared in Examples 1-4 under illumination. Figure 4 As can be seen, photoexcitation induces the generation of photogenerated carriers in α-Si, which in turn triggers an interfacial redox cycle of ferrocene methanol (MFc) on the surface of the micro-nano robot, creating an asymmetric chemical concentration gradient around the micro-nano robot, and ultimately generating diffusion force to drive the motor movement.

[0086] Figure 5 The figures show the motion of the 0D silicon-based optically driven micro / nano robot prepared in Example 1 under visible and near-infrared light. In Figure A, the migration speed of the 0D silicon-based optically driven micro / nano robot under chopper light irradiation is shown, and in Figure B, the speed of the 0D silicon-based optically driven micro / nano robot as light intensity changes is shown. These figures reveal the ability of the micro / nano robot prepared in this invention to respond to light stimulation, which is of great significance for understanding the light-driven mechanism, evaluating the performance of micro / nano robots, and optimizing their design.

[0087] Magnetic control performance test: The silicon-based light-driven micro / nanorobot suspensions prepared in Examples 5-8 were dispersed into a PDMS container placed on a glass slide, and a cover glass was used to prevent liquid flow. The container was then placed in a uniform magnetic field space, and the direction could be manipulated using a control handle. During the migration of the light-driven micro / nanorobots, the movement of the light-driven micro / nanorobots could be manipulated by the magnetic field, causing them to migrate along a specific trajectory. The silicon-based light-driven micro / nanorobots prepared in this invention achieve self-diffusion migration through a locally generated ion concentration gradient via photoelectrochemical reactions, while the addition of nickel allows for control of the migration direction via an external magnetic field. With the help of an external gradient magnetic field, precise control of the light-driven micro / nanorobots can be achieved.

[0088] Figure 6This is a diagram showing the navigation trajectory of the 0D silicon-based optically driven micro / nano robot prepared in Example 5 under an external magnetic field; the diagram depicts the micro / nano robot's trajectory in the range of 0–1 T·m. -1 The process of migrating along a specific trajectory under the influence of a gradient magnetic field demonstrates its magnetic field responsiveness and directional control precision.

[0089] Test Example 2: Phototactic Motion Test of 3D Silicon-based Optically Driven Micro / Nano Robots

[0090] This invention aims to investigate the influence mechanism of the shadow effect induced by the three-dimensional structure of a 3D silicon-based light-driven micro / nano robot on phototropic motion under illumination. During testing, the 3D silicon-based light-driven micro / nano robot prepared in Example 4 was selected. By adjusting the position and angle of the light source, the direction of illumination was changed, simulating the shadow effect generated by the 3D structure. The motion process of the 3D silicon-based light-driven micro / nano robot under different illumination conditions was recorded using a high-speed camera. Its motion trajectory and speed were tracked using video analysis software to analyze its response to illumination conditions.

[0091] Figure 8 This image shows the turning process of the 3D silicon-based light-driven micro / nano robot in Example 4 under directional light. The image records the turning process of the 3D silicon-based light-driven micro / nano robot under the influence of directional light shadow effects, confirming the feasibility of light-controlled direction. The results show that the 3D silicon-based light-driven micro / nano robot prepared in Example 4 can respond to changes in light direction and exhibits a clear positive phototaxis behavior under directional light illumination, thus clarifying its phototaxis motion law and characteristics based on structural shadow effects.

[0092] Test Example 3: Dynamic Bacterial Capture by Bacteriophage-Functionalized Micro / Nano Robots

[0093] A 20 nm thick gold layer was deposited on the surface of silicon wafers coated with the silicon-based photo-driven micro / nano robots prepared in Examples 1-3, respectively. The pretreated silicon wafers were then immersed in a 50 mM 11-mercaptoundecanoic acid (11-MUA) ethanol solution and left to stand overnight at room temperature to allow Au-S bonds to form a self-assembled monolayer (SAM) on the gold surface of the micro / nano robot. The next day, unbound 11-MUA was removed by rinsing with ultrapure ethanol, and the wafers were dried with compressed air. The wafers were then placed in a 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) / N-hydroxysuccinimide (NHS) activation system and activated at room temperature for 30 min. Subsequently, the silicon wafer surface was rinsed with deionized water, and a phage suspension (titer of 10) was immediately added to the surface of the micro / nano robot. 8 -10 11The silicon wafers were then incubated overnight at room temperature under humid conditions (PFU / mL). The next day, the wafers were removed, rinsed with deionized water to remove non-specifically bound phages, and then immersed in a 5% bovine serum albumin (BSA) solution for 30 minutes to inhibit non-specific adsorption, followed by thorough rinsing with deionized water. Finally, the functionalized 0D, 1D, and 2D silicon-based light-driven micro / nano robots were mixed with *E. coli*, and the capture effect was observed under visible light. All exhibited excellent bacterial capture performance. (See details...) Figure 9 and Figure 10 , Figure 9 The image shows the trajectory of the 0D silicon-based light-driven micro-nano robot that captured bacteria, prepared in Example 1. The image clearly shows the 0D silicon-based light-driven micro-nano robot approaching the target bacteria from its initial position. After contact, the bacteria are captured by the specific binding of surface bacteriophages. This image intuitively demonstrates the realization process of its directional movement capability and bacterial capture function under light-driven conditions. Figure 10 Image A shows the trajectory of bacteria captured by the 1D silicon-based light-driven micro / nano robot prepared in Example 2. Figure 10 Figure B shows the trajectory of the silicon-based light-driven micro-nano robot prepared in Example 3, which captures bacteria. This figure shows the targeted motion characteristics of the robot in the corresponding dimension under light drive and its effective capture effect on bacteria, which confirms the universality of the silicon-based light-driven micro-nano robot preparation method provided by the present invention in realizing the function of cross-dimensional micro-nano robots.

[0094] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a silicon-based optically driven micro / nano robot, characterized in that, Includes the following steps: First, an amorphous silicon thin film is deposited on the surface of a substrate material. Then, a metal layer is prepared on the amorphous silicon thin film by magnetron sputtering. Finally, a nickel metal film is deposited on the surface of the metal to obtain the silicon-based optically driven micro / nano robot. The deposition process is plasma-enhanced chemical vapor deposition (PECVD). The parameters for PECVD include: operating frequency of 13.56 MHz, pressure of 0.5–5 Torr, gases of silane and argon, gas flow rate of 300–1000 sccm, and deposition rate of 40–60 nm·min. -1 ; The metal is a metal that matches the band gap of the amorphous silicon thin film.

2. The method for fabricating silicon-based optically driven micro / nano robots according to claim 1, characterized in that, The matrix material is selected from zero-dimensional materials, one-dimensional materials, two-dimensional materials, or three-dimensional materials.

3. The method for fabricating silicon-based optically driven micro / nano robots according to claim 1, characterized in that, The metal is gold or platinum.

4. A silicon-based optically driven micro / nano robot, characterized in that, The silicon-based optically driven micro / nano robot is prepared by the preparation method described in any one of claims 1 to 3 and has any one of zero-dimensional, one-dimensional, two-dimensional or three-dimensional structures.

5. The silicon-based optically driven micro / nano robot according to claim 4, characterized in that, When the silicon-based optically driven micro / nano robot includes an amorphous silicon thin film and a metal layer, the thickness of the amorphous silicon thin film is 240 nm and the thickness of the metal layer is 10 nm. When the silicon-based optically driven micro / nano robot comprises an amorphous silicon thin film, a metal layer, and a nickel metal film, the thickness of the amorphous silicon thin film is 240 nm, the thickness of the metal layer is 10 nm, and the thickness of the nickel metal film is 20 nm.

6. The application of a silicon-based light-driven micro / nano robot as described in claim 4 or 5 in the preparation of products for capturing bacteria, neural modulation, and drug delivery.

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