Miniature sewage purification robot based on algal-bacterial symbiotic system and preparation method thereof

Abstract

The invention discloses a micro sewage purification robot based on an algal-bacterial symbiotic system and a preparation method of the micro sewage purification robot. The robot comprises a spiral carrier used for carrying the algal-bacterial symbiotic system, a swim-ring-shaped protective shell and a biological coating on the surface of the spiral carrier, and is characterized in that the section of the spiral carrier is of a star-shaped distribution structure, and the axis of the spiral carrier is hollow; microalgae are implanted into the spiral carrier; a fibronectin coating on which bacteria are attached is arranged on the surface of the spiral carrier; the device is provided with a swim ring-shaped protective shell. Through the design of the spiral carrier and the fibronectin coating, the attachment area and attachment firmness of bacteria on the carrier are increased, the pollutant decomposition efficiency of the algal-bacterial symbiotic system is improved, and the carrier has small resistance when moving in water; the protective shell structure prevents the carrier from being physically damaged, the service life of the robot is prolonged, meanwhile, the spiral carrier and the protective shell are formed by photocuring printing of degradable hydrogel materials, and environmental friendliness is achieved.

Description

Technical Field

[0001] The present invention relates to the fields of micro-robots and environmental science and technology. Specifically, it relates to a micro sewage purification robot based on an algal-bacterial symbiotic system and a preparation method thereof, which is particularly suitable for small spaces where large sewage purification devices cannot be installed and the treatment of eutrophic water bodies in rivers and lakes. Background Art

[0002] With the rapid development of industrialization and urbanization, the problem of water pollution has become increasingly serious. In particular, the eutrophication phenomenon caused by excessive nutrients such as nitrogen and phosphorus has become the focus of global attention. Traditional sewage treatment methods mostly rely on physical filtration, chemical precipitation, and biological treatment. However, these methods often have problems such as high costs, complex operations, and potential secondary pollution. Taking the fixed algal-bacterial symbiotic system as an example, its carrier materials are mostly non-degradable plastics or metals and the device scale is large, which not only increases the environmental burden but also limits the flexibility and adaptability of the system. In addition, due to the limitations of the material and surface treatment method of the existing carrier, the bacterial attachment efficiency is low, resulting in insufficient pollutant removal efficiency. In recent years, researchers have begun to explore the possibility of using the algal-bacterial symbiotic system in nature for sewage treatment. This method can not only effectively remove harmful substances in the water body but also has the characteristics of environmental friendliness.

[0003] At present, certain progress has been made in the sewage treatment technology based on the algal-bacterial symbiotic system. Existing research has pointed out that the algal-bacterial symbiotic system (ABSS) can effectively remove nutrients, antibiotics, and heavy metals in sewage. However, the traditional algal-bacterial symbiotic system usually relies on a fixed reactor structure, which limits its application scope and flexibility. In addition, these systems often require specific operating conditions, such as sufficient light and oxygen supply, which are difficult to achieve for some complex water environments. More importantly, the fixed reactors cannot flexibly adapt to the specific conditions of different water areas and cannot quickly respond to sudden pollution incidents.

[0004] To overcome the above problems, researchers have tried to apply the algal-bacterial symbiotic system to micro-carriers to improve the treatment efficiency and adaptability. For example, some studies have shown that by immobilization technology, bacteria and microalgae can be combined in a specific carrier in a certain proportion, which can effectively improve the pollutant removal effect. However, for large-scale water area treatment, the cost and operation complexity are still the main obstacles. At the same time, the immobilized carrier materials often do not have degradability and may cause secondary pollution problems. In addition, these fixed devices lack mobility and cannot be quickly deployed to the polluted area according to actual needs, greatly limiting their application scope.

[0005] Taking the most common immobilization carrier in the prior art as an example, although such carriers can promote the formation of the bacteria-algae symbiotic system to a certain extent, there are still significant defects in the actual application process. First, due to the unreasonable hardness and shape design of the carrier material, the stability of the bacteria-algae symbiotic system may be poor, and it is easily damaged by water flow impact and fails. Second, the surface of the existing carrier is usually smooth, which is not conducive to the attachment and growth of bacteria, affecting the efficiency of the symbiotic system. Finally, under the existing technical conditions, in order to better support the bacteria-algae symbiosis, the carrier material often selects some materials that are difficult to be degraded and absorbed, increasing the risk of secondary pollution. More importantly, these immobilized devices cannot move and cannot be flexibly adjusted according to the actual situation, thus limiting their application in dynamic environments.

[0006] To support the bacteria-algae symbiosis, the carrier material often selects some materials that are difficult to be degraded and absorbed, increasing the risk of secondary pollution. More importantly, these immobilized devices cannot move and cannot be flexibly adjusted according to the actual situation, thus limiting their application in dynamic environments.

[0007] In summary, if a new structure, new material, and micro-sized movable micro sewage purification robot solution can be proposed to overcome many defects in the prior art, then its use effect will be greatly improved, ensuring the smooth progress of efficient and environmentally friendly water purification operations. Summary of the Invention

[0008] The object of the present invention is to propose a micro sewage purification robot based on the bacteria-algae symbiotic system and its preparation method to solve the problems existing in the above prior art, so that the micro robot has the ability to carry an efficient bacteria-algae symbiotic system, can be flexibly deployed to the water area to be treated, and has higher stability and longer working life.

[0009] To achieve the above object, the present invention provides the following solution: The present invention provides a micro robot, including:

[0010] A spiral carrier, the spiral carrier is located in a protective shell, and its central axis coincides with the central axis of the protective shell. There are a total of five spiral blades; the spiral cross-section adopts a star-shaped distribution structure; the surface of the spiral blade is designed with a pit structure; the spiral carrier can provide a large area for bacteria attachment, while maintaining good hydrodynamic performance, ensuring that the water flow can be effectively guided when passing through the spiral carrier and fully contacting with the bacteria and algae.

[0011] Preferably, the spiral carrier is a circular spiral structure connected end to end, with 5-7 turns of the spiral, the central radius of the spiral is 8mm-12mm, the inner end radius is 6mm-8mm, the outer end radius is 12-14mm, and the pitch is 3mm-5mm;

[0012] Preferably, the width of the cross-section of the spiral blade is 0.5mm-0.8mm, and the length is 1.5mm-2.0mm.

[0013] Preferably, the spiral carrier has a central hole, which is embodied in that a regular hexagon structure is provided at the center of the cross-section, and the side length is 1.8 mm.

[0014] Preferably, three rows of pit structures are provided on each side of the surface of each spiral blade, and each row contains 300 pits.

[0015] Preferably, the width of each pit is 0.4 mm and the depth is 0.2 mm.

[0016] A protective shell, the protective shell adopts a toroidal shape to ensure that the robot can float stably in water and withstand external impacts; 8 hollow holes are provided on the surface of the protective shell to improve water flow through and reduce weight. The shape of the hollow holes is composed of two arcs and two common tangents. The hollow design not only improves the air permeability of the overall structure but also ensures the smooth flow of water inside the spiral carrier.

[0017] Preferably, the wall thickness of the protective shell is 0.6 mm - 1.0 mm, the outer end radius is 8 mm - 12 mm, and the inner end radius is 4 mm - 8 mm.

[0018] Preferably, the diameter of the large arc of the hollow hole is 2.0 mm - 3.0 mm, the diameter of the small arc is 1.4 mm - 2.0 mm, and the distance between the two centers is 5.0 mm - 6.0 mm.

[0019] Preferably, the distance between the inner end of the spiral carrier and the inner wall of the protective shell is 2.0 mm - 2.5 mm.

[0020] A biological coating, the biological coating is covered on the surface of the spiral carrier by physical adsorption, and the bacteria in the bacteria-algae symbiotic system adhere to the biological coating in the form of a biofilm

[0021] Preferably, the biological coating is a fibronectin coating

[0022] Preferably, the concentration of the biological coating on the surface of the spiral carrier is 1 - 5 micrograms per square centimeter

[0023] The present invention also discloses a processing method for coating the above biological coating on a spiral carrier, including the following steps:

[0024] S1. Dissolve fibronectin to obtain a fibronectin solution.

[0025] S2. Add fibronectin to PBS buffer to obtain a coating solution.

[0026] S3. Immerse the cured spiral carrier in the coating solution and incubate.

[0027] S4. After the incubation of the spiral carrier, rinse it with PBS buffer multiple times to remove the excess fibronectin.

[0028] Meanwhile, the present invention also provides a processing method for forming a biofilm on the surface of a hydrogel carrier by nitrifying bacteria, comprising the following steps:

[0029] S1. Immerse the spiral carrier covered with a fibronectin coating in a nitrifying bacteria suspension.

[0030] S2. Let the nitrifying bacteria solution containing the spiral carrier stand at room temperature for 1 hour, and gently shake it during this period.

[0031] S3. After the bacteria attachment is completed, rinse it again with PBS buffer to remove the unattached bacteria.

[0032] The present invention also provides a preparation method of the above-mentioned micro-robot: by means of ultraviolet light curing, the spiral carrier and the protective shell are respectively printed using different degradable hydrogels, and the spiral carrier is coated with a biological coating and attached with bacteria.

[0033] The present invention has the following beneficial effects compared with the prior art:

[0034] Through the design of the spiral carrier, a larger surface area is provided, increasing the attachment points of algae, promoting the flow of fluids, improving the exchange efficiency of nutrients and oxygen, and being able to utilize space more effectively than traditional spherical or block-shaped carriers, reducing dead angles, enhancing the mass transfer efficiency of the overall system, and contributing to the activity and growth rate of microscale microalgae. The coating of the biological coating further enhances the stability of bacteria attached to the surface of the carrier, giving the robot a longer working life. At the same time, the protective shell formed by light-curing printing can provide protection for the carrier, preventing damage to the internal bacteria-algae symbiotic system by the external environment. In addition, the whole robot is made by means of hydrogel light-curing printing, which has degradability and reduces the possibility of secondary environmental pollution. The micro-robot proposed by the present invention can be flexibly deployed into various sewage environments, with strong adaptability and convenience.

[0035] Finally, the present invention also provides a reference for other technical solutions related to sewage treatment micro-robots, which can be extended and studied in depth based on this, and the overall solution has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings constituting a part of this application are used to provide a further understanding of this application, making other features, objects, and advantages of this application more obvious. The schematic embodiments and descriptions of the drawings of this application are used to explain this application and do not constitute an improper limitation to this application. In the drawings:

[0037] Figure 1 is an axonometric view of the micro-robot provided by the embodiment of the present invention;

[0038] Figure 2 The top view of the micro-robot provided by the embodiment of the present invention;

[0039] Figure 3 The front view of the micro-robot provided by the embodiment of the present invention;

[0040] Figure 4 The sectional view of the micro-robot provided by the embodiment of the present invention;

[0041] Figure 5 The axonometric view of the spiral carrier structure in the micro-robot provided by the embodiment of the present invention;

[0042] Figure 6 A part intercepted from the spiral carrier structure included in the micro-robot provided by the embodiment of the present invention;

[0043] Figure 7 The schematic diagram of material exchange of the bacteria-algae symbiotic system carried by the micro-robot provided by the embodiment of the present invention.

[0044] Wherein: 1. The housing of the protective shell; 2. The hollow holes of the protective shell; 3. The spiral carrier; 4. The hollow structure in the spiral carrier; 5. The pits on the surface of the spiral carrier; 6. The fibronectin coating on the surface of the spiral carrier; 7. The external water environment; 8. The fibronectin coating on the surface of the spiral carrier; 9. The hydrogel part of the spiral carrier; 10. The bacteria attached to the surface of the spiral carrier; 11. The chlorella contained inside the spiral carrier. Detailed implementation manners

[0045] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0046] The present invention discloses a micro sewage purification robot based on a bacteria-algae symbiotic system and its preparation method. The specific solutions are as follows.

[0047] On the one hand, the micro-robot of the present invention can be applied to the field of sewage purification. According to its working principle, a spiral carrier is provided. In terms of its structure, it includes a spiral carrier, a protective shell, and a biological coating. The main function of the spiral carrier is to carry a bacteria-algae symbiotic system and achieve an efficient sewage purification function through its unique structural design.

[0048] Such as Figure 1-3As shown, the protective shell 1 adopts a toroidal structure similar to the shape of a swimming ring, surrounding the outside of the spiral carrier, having a large surface area and reasonable hydrodynamic characteristics. There are 8 hollow holes 2 provided on the surface for improving water flow throughability and reducing weight. Its material is a degradable hydrogel, and this material selection aims to reduce secondary pollution to the environment.

[0049] In the embodiment, the outer end radius of the protective shell 1 is 8 mm - 12 mm, preferably 10 mm; the inner end radius is 4 mm - 8 mm, preferably 6 mm; the wall thickness is 0.6 mm - 1.0 mm, preferably 0.6 mm.

[0050] In the embodiment, the diameter of the large arc of the hollow surface forming the hollow hole 2 is 2.0 mm - 3.0 mm, preferably 2.4 mm; the diameter of the small arc is 1.4 mm - 2.0 mm, preferably 1.6 mm; the distance between the two centers is 5 mm - 6 mm, preferably 5.6 mm.

[0051] As Figure 5-6 shown, in order to enable the micro-robot to have a high purification efficiency in a sewage environment, the spiral carrier 3 adopts a star-shaped distributed cross-section design, consisting of five spiral blades, with a hole 4 at the center, and there are pits 5 on the surface of the carrier. This design not only increases the surface area of the carrier, but also provides more attachment points for nitrifying bacteria, thereby improving the overall efficiency of the bacteria-algae symbiotic system. At the same time, it ensures good hydrodynamic performance, ensuring that the water flow can be effectively guided when passing through the spiral carrier and fully contacting with the bacteria and algae.

[0052] In this embodiment, the spiral carrier 3 is a ring-shaped spiral structure with the head and tail connected, the number of spiral turns is 5 - 7 turns, preferably 6 turns; the central radius of the spiral is 8 mm - 12 mm, preferably 10 mm; the inner end radius is 6 mm - 8 mm, preferably 7 mm; the outer end radius is 12 - 14 mm, preferably 13 mm, and the pitch is 3 mm - 5 mm, preferably 4 mm.

[0053] In this embodiment, the width of the cross-section of the spiral blade is 0.5 mm - 0.8 mm, preferably 0.6 mm; the length is 1.5 mm - 2.0 mm, preferably 1.8 mm; the width of the pit 5 is 0.4 mm and the depth is 0.2 mm.

[0054] In this embodiment, the central hole 4 is a regular hexagon with a side length of 1.8 mm.

[0055] In this embodiment, the biological coating 6 coated on the surface of the spiral carrier is a fibronectin coating, and the coating concentration is 3 μg / cm 2This concentration is optimized to ensure that nitrifying bacteria can firmly attach, while not overly occupying the area for bacterial attachment. The fibronectin coating is fixed on the surface of the spiral carrier through physical adsorption, even if the printed spiral carrier is immersed in the fibronectin solution for 60 minutes. This gentle fixation method not only improves the attachment efficiency of bacteria but also ensures that no other chemical substances or physical methods affect the survival of algae in the spiral carrier, enhancing the biocompatibility of the carrier and making it more suitable for working in complex sewage environments.

[0056] Furthermore, for the micro-robot described in this embodiment, the star-shaped cross-sectional design of its spiral carrier significantly increases the surface area of the carrier, providing more attachment points for nitrifying bacteria. This design not only optimizes space utilization but also improves the activity and growth rate of microorganisms, thereby further enhancing the sewage purification efficiency. The swimming ring shape design of the protective shell can effectively buffer external impacts and prevent the carrier from being physically damaged in a complex sewage environment. At the same time, the design of the water-permeable holes allows pollutants in the sewage to enter the interior of the carrier, promoting mass exchange and achieving efficient sewage purification. The outer diameter, length of the spiral carrier, and the tooth height and tooth pitch of the star-shaped cross-section are optimized to maximize the mass exchange efficiency. At the same time, this optimized design enables the micro-robot to maintain a low resistance when moving in sewage, improving work efficiency. The thickness, inner diameter, and outer diameter of the protective shell are precisely designed to ensure its tight fit with the spiral carrier. This design not only improves the overall stability of the robot but also ensures its adaptability in complex environments.

[0057] In summary, the micro-robot of the present invention, through the design of the spiral carrier and the protective shell, significantly improves the sewage purification efficiency, reduces the movement resistance, and extends the service life of the robot.

[0058] In addition, the micro-robot of the present invention uses a biodegradable hydrogel material, reducing secondary pollution to the environment and having broad application prospects.

[0059] In terms of the bacteria-algae symbiotic system, the Chlorella carried by the micro-robot in this embodiment is a highly efficient photosynthetic microorganism that can use light energy to convert carbon dioxide and water into organic substances (such as glucose) and release oxygen. This process not only provides energy for its own growth but also provides the necessary oxygen for the symbiotic nitrifying bacteria. Chlorella itself can also absorb nutrients such as nitrogen and phosphorus in the water, reducing the eutrophication phenomenon in the water body. In addition, they can also absorb some heavy metal ions to further purify the water quality. And nitrifying bacteria are a class of bacteria that can oxidize ammonia (NH3) to nitrite (NO2 - ) and then further oxidize it to nitrate

[0060] (NO3 -Microorganisms of ( ). This process not only helps remove ammonia nitrogen pollution in water, but also provides an available nitrogen source for Chlorella vulgaris.

[0061] On the other hand, the present invention also discloses a preparation method of the micro-robot as described above, comprising the following steps:

[0062] S1. Prepare the hydrogel solutions for the spiral carrier and the protective shell respectively.

[0063] Among them, S1 includes:

[0064] S11. Prepare the spiral carrier hydrogel: Weigh 10% (w / v) of methacrylated gelatin (GelMA) and 5% (w / v) of polyethylene glycol diacrylate (PEGDA) respectively. Dissolve GelMA in PBS buffer solution, stir evenly and then add PEGDA, and continue to stir until completely dissolved.

[0065] S12. Add the photoinitiator Irgacure 2959 and continue to stir until evenly dispersed. The addition amount of the photoinitiator is 0.5% (w / v) of the total amount of the hydrogel solution to ensure rapid curing and molding under ultraviolet light irradiation.

[0066] S13. Use a vacuum degassing device to remove the bubbles in the solution to ensure that no bubble defects will occur during the printing process.

[0067] S14. Add the Chlorella vulgaris suspension and gently stir to make it evenly distributed, avoiding cell damage.

[0068] S15. Prepare the protective shell hydrogel: Weigh 20% (w / v) of methacrylated gelatin (GelMA) and 30% (w / v) of polyethylene glycol diacrylate (PEGDA) respectively. Dissolve GelMA in PBS buffer solution, stir evenly and then add PEGDA, and continue to stir until completely dissolved.

[0069] S16. Add the photoinitiator Irgacure 2959 and continue to stir until evenly dispersed. The addition amount of the photoinitiator is 1% (w / v) of the total amount of the hydrogel solution to ensure rapid curing and molding under ultraviolet light irradiation.

[0070] S17. Use a vacuum degassing device to remove the bubbles in the solution to ensure that no bubble defects will occur during the printing process.

[0071] S2. Print the lower half of the protective shell by a photocuring method. Pour the protective shell solution into the material tank of the photocuring printer, and use an ultraviolet light source to expose and cure layer by layer, and the exposure time for each layer is 4 - 6 seconds.

[0072] Among them, S2 includes:

[0073] S21. Uniformly drop the protective shell solution onto the printing platform of the light-curing printer, and start printing the lower half of the protective shell layer by layer.

[0074] S22. After printing is completed, carefully remove the lower half of the protective shell from the printing platform and soak it in deionized water for 10 minutes to remove uncured residues.

[0075] S3. Print the spiral carrier by the light-curing method. Pour the spiral carrier solution into the material tank of the light-curing printer, and use the same ultraviolet light source to expose and cure layer by layer, with the exposure time for each layer being 4 - 6 seconds.

[0076] Among them, S3 includes:

[0077] S31. Uniformly drop the spiral carrier solution onto the printing platform of the 3D printer, and start printing the spiral carrier layer by layer.

[0078] S32. After printing is completed, carefully remove the spiral carrier from the printing platform and soak it in deionized water for 10 minutes to remove uncured residues. During this period, ensure that the environmental temperature is 20°C - 30°C to ensure the activity of Chlorella.

[0079] S4. Immerse the spiral carrier in the biological coating solution to form a biological coating.

[0080] Among them, S4 includes:

[0081] S41. Immerse the cured spiral carrier in the fibronectin solution and incubate it at room temperature for 1 hour to ensure that fibronectin adheres uniformly to the surface of the carrier.

[0082] S42. After incubation, rinse the carrier with PBS buffer multiple times to remove excess fibronectin and ensure the uniformity and stability of the biological coating.

[0083] S5. Immerse the spiral carrier coated with the biological coating in the nitrifying bacteria solution to make the nitrifying bacteria adhere. Immerse the spiral carrier with the fibronectin coating in the nitrifying bacteria suspension (concentration: 10^8 CFU / mL) and let it stand at room temperature for 1 hour.

[0084] Among them, S5 includes:

[0085] S51. During the soaking process, gently shake the container to promote the uniform distribution of nitrifying bacteria and their adhesion to the fibronectin coating.

[0086] S52. After adhesion is completed, rinse the carrier with PBS buffer again to remove unadhered bacteria and ensure the uniform and firm adhesion of bacteria on the surface of the carrier.

[0087] S6. Place the spiral carrier with attached nitrifying bacteria into the half-printed protective shell and complete the printing of the other half of the protective shell.

[0088] Among them, S6 includes:

[0089] S61. Place the processed spiral carrier into the lower half of the protective shell.

[0090] S62. Continue to use the photocuring method to print the upper half of the protective shell to ensure that the protective shell completely wraps the spiral carrier to form a complete micro-robot structure.

[0091] After printing, remove the entire micro-robot from the printing platform and soak it in deionized water for 10 minutes to remove uncured residues.

[0092] Take the micro-robot out of the water, rinse it with PBS buffer solution, and complete the preparation of the micro-robot.

[0093] The preparation method of the present invention provides a reference for other technical solutions related to micro-robots, and can be extended and studied in depth based on this. The overall solution has a very broad application prospect.

[0094] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit and basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention. Finally, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A micro sewage purification robot based on a bacterial-algal symbiotic system and a preparation method thereof, characterized in that ,include: A spiral carrier (3), wherein the spiral carrier (3) is a ring-shaped spiral structure connected head to tail, and its cross section is a star-shaped distribution structure formed by five rectangular spiral blades, and a regular hexagonal hollow structure (4) is provided at the axis; A swimming ring-shaped protective shell (1), the protective shell (1) surrounds the spiral carrier (3) and the central axes of the two coincide with each other, and a through-type hollow hole (2) is provided between the inner end and the outer end of the protective shell; A biological coating (6), wherein the biological coating (6) is a fibronectin coating, which is coated on the surface of the spiral carrier (3) by a physical adsorption method and is used to fix nitrifying bacteria (10); The microalgae (11) is Chlorella vulgaris, which is implanted in the spiral carrier (3) and forms a bacteria-algae symbiotic system with the nitrifying bacteria (10).

2. The microrobot according to claim 1, characterized in that: The spiral carrier (3) has 5 to 7 spiral turns, a spiral center radius of 8 mm to 12 mm, an inner radius of 6 mm to 8 mm, an outer radius of 12 mm to 14 mm, and a spiral pitch of 3 mm to 5 mm.

3. The micro robot according to claim 2, characterized in that: The cross section of the spiral carrier (3) is a star-shaped distribution structure formed by five rectangular spiral blades, the thickness of the spiral blades is 0.5 mm-0.8 mm, and the length is 1.5 mm-2.0 mm.

4. The microrobot according to claim 2, characterized in that: Three rows of pit structures (5) are respectively provided on both sides of the surface of each spiral blade, each row contains 300 pits, and the width of the pits is 0.3mm-0.5mm and the depth is 0.2mm-0.3mm.

5. The micro robot according to claim 1, characterized in that: The protective shell (1) is in the shape of a torus similar to a swimming ring, with an outer end radius of 8mm-12mm, an inner end radius of 4mm-8mm, and a wall thickness of 0.6mm-1.0mm.

6. The microrobot according to claim 5, characterized in that: There is a through hollow structure (2) between the inner and outer ends of the protective shell (1), the number of hollows is 8-12, the shape of the hollow is composed of two arcs and two common tangents, the size of each hollow hole is a large arc diameter of 2.0mm-3.0mm, a small arc diameter of 1.4mm-2.0mm, and the distance between the two centers is 5mm-6mm.

7. The microrobot according to claim 1, characterized in that: The spiral carrier (3) is located inside the protective shell (1), the central axis of the spiral carrier (3) coincides with the central axis of the protective shell (1), and the inner end of the spiral is 2.0 mm to 2.5 mm away from the inner wall of the protective shell.

8. The micro robot according to claim 1, characterized in that: The biological coating (6) is a fibronectin coating, which is coated on the surface of the spiral carrier (3) by a physical adsorption method.

9. The microrobot according to claim 1, characterized in that: The bacteria in the bacteria-algae symbiotic system are nitrifying bacteria, and the microalgae are Chlorella.

10. A method for preparing a microrobot as claimed in any one of claims 1 to 9, comprising the following steps: S1. Prepare hydrogel prepolymer solutions of the protective shell (1) and the spiral carrier (3), respectively, wherein the concentration of methacrylated gelatin (GelMA) in the hydrogel solution is 10%-20% (w / v), the concentration of polyethylene glycol diacrylate (PEGDA) is 5%-10% (w / v), and the amount of photoinitiator Irgacure2959 added is 0.5%-1% (w / v) of the total amount of the hydrogel solution; S2, using UV curing 3D printing technology to print the lower part of the protective shell (1) layer by layer with an exposure time of 4-6 seconds per layer; S3, using ultraviolet light curing 3D printing technology to print the spiral carrier (3) layer by layer with an exposure time of 4-6 seconds per layer; S4, immersing the solidified spiral carrier (3) in a biological coating solution, incubating at room temperature for 1 hour to form a biological coating (6), wherein the biological coating solution is a fibronectin solution, and the concentration of the formed biological coating (6) on the surface of the spiral carrier (3) is 1-5 micrograms per square centimeter; S5, soaking the spiral carrier (3) covered with the biological coating in a nitrifying bacteria solution with a concentration of 10^8 CFU / ml, leaving it to stand for one hour to allow the nitrifying bacteria (10) to attach and form a biofilm. The carrier was washed several times with PBS buffer; S6. Slowly place the spiral carrier (3) with attached nitrifying bacteria (10) into the lower half of the printed protective shell (1) in PBS buffer, and print the other half of the protective shell layer by layer again with an exposure time of 4-6 seconds per layer.

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