4D printing bionic soft robot driven by near-infrared light and used for underwater operation

Abstract

The invention belongs to the field of bionic soft robots, and particularly relates to a near-infrared light driven 4D printing bionic soft robot for underwater operation, and a preparation method of the near-infrared light driven 4D printing bionic soft robot comprises the following steps: adding graphene oxide into water, and carrying out ultrasonic treatment; adding an N-isopropylacrylamide monomer, N, N '-methylene bisacrylamide and phenyl (2, 4, 6-trimethylbenzoyl) lithium phosphate, and carrying out ultrasonic treatment; adding lithium bentonite to obtain ink; quickly stirring until the ink is inverted and does not flow to obtain the GO-NIPAM ink capable of being used for 3D printing; the GO-NIPAM ink is loaded into a charging barrel for 3D printing, a 3D printing model is of a starfish-imitating structure, and the GO-NIPAM ink of the starfish-imitating structure is obtained; ultraviolet light is used for curing, and GO-PNH hydrogel is obtained; and soaking in a 0.1-0.3 M hydrazine hydrate aqueous solution, and then soaking in deionized water to obtain the 4D printing bionic soft robot based on rGO-PNH. The 4D printing bionic soft-bodied robot has quick, stable and repeatable near-infrared light response, can execute grabbing and releasing actions, and can adapt to an underwater working environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of bionic soft robots, and particularly relates to a 4D printing bionic soft robot driven by near-infrared light for underwater operations. Background Art

[0002] During billions of years of evolution, organisms in nature have the ability to sense changes in the surrounding environment and make feedback by adjusting themselves. For example, a large number of crystals are distributed on the echinoderm skin of starfish, and starfish can sense the surrounding environment through these crystals to adjust themselves (such as camouflage or predation, etc.); at the same time, the arms of starfish are covered with tentacles, and these tentacles have the ability to stretch and contract, which can help starfish move, forage and grasp objects on the seabed. Organisms in nature have provided many inspirations for the preparation of intelligent artificial systems that can sense the external environment and make corresponding responses. Among them, intelligent robots are a typical example. Although intelligent robots have the potential to assist or even replace humans in dangerous, laborious and complex tasks, traditional rigid robots require pre-programming and motor drive, and often contain complex and bulky electronic systems. In addition, the performance of rigid robots in complex environments is also not satisfactory, and they cannot adapt to complex shapes and dynamic changes in the environment. On the contrary, soft robots show extraordinary flexibility, and soft robots prepared from intelligent responsive materials also have good adaptability to complex environments.

[0003] Hydrogels have the unique property of being insoluble in water and can effectively function in an aqueous environment. Intelligent hydrogels can respond to stimuli such as light, temperature, humidity, pH value, and electric / magnetic fields. The thermosensitive poly(N-isopropylacrylamide) hydrogel (PNH) formed by the polymerization of N-isopropylacrylamide has the characteristics of swelling and absorbing water below the lower critical solution temperature (LCST, ~33 °C) and shrinking and losing water above the LCST. At present, some researchers have prepared light-responsive hydrogels by combining photothermal conversion materials with thermosensitive hydrogels. However, the traditional mold method for preparing intelligent hydrogels has a single style, and the manufacturing cost increases sharply with the increase in the complexity of the shape. 3D printing technology has received extensive attention due to its high efficiency, strong designability, one-piece molding, simplicity and convenience, etc. However, traditional 3D printing is limited to creating static samples and often needs to be combined with photocuring, with high requirements for the light transmittance of the material. 4D printing technology involves using 3D printing methods to construct specific structures, and the obtained structural products can make corresponding responses according to external stimuli. The inherent responsiveness of intelligent hydrogels to the surrounding environment makes them meet the requirements of 4D printing for materials. Based on this, some researchers have successfully obtained 4D printing products with environmental responsiveness by 3D printing intelligent hydrogels. However, there is no report in the prior art on how to successfully prepare a soft robot with fast, stable and repeatable near-infrared light response, capable of performing grasping and releasing actions, and adaptable to the underwater operation environment. Summary of the Invention

[0004] Technical Problem: To provide a preparation method of a soft robot that has a fast, stable, and repeatable near-infrared light response, can perform grasping and releasing actions, and can adapt to the underwater operation environment.

[0005] Technical Concept: This application takes the marine soft organism starfish as the inspiration source, and uses a thermosensitive hydrogel as the deformable matrix of the soft robot, enabling it to flexibly adapt to various complex environmental changes underwater. The bionic soft robot is realized through 3D printing. In this application, by optimizing the photothermal conversion material and screening the hydrogel system, rGO-PNH hydrogel is obtained. The relative dosages of graphene oxide: N-isopropylacrylamide monomer: N,N'-methylenebisacrylamide: lithium phenyl(2,4,6-trimethylbenzoyl)phosphate, and the relative dosage of lithium bentonite are optimized, etc., so that it not only has fast and stable light response characteristics but also can meet the rheological requirements of the ink for 3D printing; the preparation process of rGO-PNH hydrogel is optimized, that is, by first preparing GO-PNH hydrogel and then reducing it with hydrazine hydrate to obtain rGO-PNH hydrogel. Finally, a soft robot with a fast, stable, and repeatable near-infrared light response, capable of performing grasping and releasing actions, and adaptable to the underwater operation environment is successfully prepared. By irradiating one side of the soft robot with near-infrared light, its temperature rises above the LCST of the hydrogel and loses water and shrinks, thereby triggering mechanical movement. This light response ability provides new ways and means for the precise control and regulation of the soft robot, enhancing its adaptability and functionality in the water environment.

[0006] Technical Solution:

[0007] On the one hand, a preparation method of a 4D printing bionic soft robot driven by near-infrared light for underwater operation is provided, which includes the following steps:

[0008] (1) Add graphene oxide to water and ultrasonicate to obtain a graphene oxide dispersion;

[0009] (2) Add N-isopropylacrylamide monomer, N,N'-methylenebisacrylamide, and lithium phenyl(2,4,6-trimethylbenzoyl)phosphate to the graphene oxide dispersion obtained in step (1) and ultrasonicate to obtain a GO-NIPAM dispersion; in the GO-NIPAM dispersion, the dosage ratio of graphene oxide: N-isopropylacrylamide monomer: N,N'-methylenebisacrylamide: lithium phenyl(2,4,6-trimethylbenzoyl)phosphate is 15 mg: (4 - 5) mmol: (0.013 - 0.017) mmol: (0.074 - 0.078) mmol;

[0010] (3) Add lithium bentonite to the GO-NIPAM dispersion obtained in step (2) to obtain an ink; quickly stir until the ink does not flow when inverted to obtain a GO-NIPAM ink that can be used for 3D printing; wherein, the dosage of lithium bentonite is 0.08 - 0.1 g·mL -1 ;

[0011] (4) Load the GO-NIPAM ink obtained in step (3) into a cartridge and perform 3D printing, wherein the 3D printing model has a starfish-like structure to obtain a GO-NIPAM ink with a starfish-like structure;

[0012] (5) Cure the printed GO-NIPAM ink with a starfish-like structure obtained in step (4) using ultraviolet light to obtain a GO-PNH hydrogel;

[0013] (6) Immerse the GO-PNH hydrogel obtained in step (5) in an aqueous hydrazine solution with a concentration of 0.1 - 0.3 M to obtain an rGO-PNH hydrogel;

[0014] (7) Immerse the rGO-PNH hydrogel obtained in step (6) in deionized water to remove impurities, and then a 4D printing bionic soft robot based on rGO-PNH can be obtained.

[0015] In some embodiments, in step (2), in the graphene oxide / N-isopropylacrylamide dispersion, the dosage ratio of graphene oxide:N-isopropylacrylamide monomer:N,N'-methylenebisacrylamide:phenyl(2,4,6-trimethylbenzoyl)phosphate lithium salt is 15 mg:4.5 mmol:0.015 mmol:0.076 mmol.

[0016] In some embodiments, in step (3), the dosage of lithium bentonite is 0.09 g·mL -1 。

[0017] In some embodiments, in step (3), the mass ratio of lithium bentonite to graphene oxide is 18:1.

[0018] In some embodiments, in step (1), in the graphene oxide dispersion, the ratio of graphene oxide to water is 5 g:1 L.

[0019] In some embodiments, in step (6), the concentration of the aqueous hydrazine solution is 0.2 M, and the soaking time in the aqueous hydrazine solution is 12 h.

[0020] In some embodiments, in step (5), the ultraviolet light curing time is 100 - 180 s.

[0021] In some embodiments, in step (5), the ultraviolet light curing time is 140 s.

[0022] On the other hand, a 4D printed bionic soft robot for underwater operations driven by near-infrared light, prepared by the aforementioned preparation method, is provided.

[0023] In another aspect, there is provided an application of the aforementioned 4D printed bionic soft robot driven by near-infrared light for underwater operation in underwater operation, which comprises the following steps:

[0024] The aforementioned 4D printed bionic soft robot driven by near-infrared light for underwater operations is fixed on a rod-shaped object to control the orientation of the 4D printed bionic soft robot; one side of the 4D printed bionic soft robot is irradiated with near-infrared light so that the 4D printed bionic soft robot completes a grasping action.

[0025] Beneficial effects:

[0026] 1. This application uses the marine soft organism starfish as inspiration, and uses thermosensitive hydrogel as the deformable matrix of the soft robot, so that it can flexibly adapt to various complex environmental changes underwater. The bionic soft robot realizes its structure through 3D printing. This application selects rGO-PNH hydrogel by optimizing the photothermal conversion material and hydrogel system, optimizes the relative amount of graphene oxide: N-isopropylacrylamide monomer: N, N'-methylenebisacrylamide: phenyl (2,4,6-trimethylbenzoyl) lithium phosphate, the relative amount of lithium bentonite, etc., so that it can adapt to the rheological requirements of 3D printing for ink while having fast and stable light response characteristics; optimizes the preparation process of rGO-PNH hydrogel, that is, by first preparing GO-PNH hydrogel, and then reducing it with hydrazine hydrate to obtain rGO-PNH hydrogel, and finally successfully prepares a soft robot with fast and stable repeatable near-infrared light response, capable of performing grasping and releasing actions, and adaptable to underwater working environments. By irradiating one side of the soft robot with near-infrared light, the temperature of the hydrogel rises above the LCST, causing it to lose water and shrink, thereby triggering mechanical movement. This light-responsiveness provides a new way and means for the precise control and regulation of soft robots, enhancing their adaptability and functionality in water environments.

[0027] 2. The method for preparing a 4D printed bionic soft robot driven by near-infrared light for underwater operations of the present application can simply and efficiently prepare a 4D printed bionic soft robot with fast near-infrared light response.

[0028] 3. The preparation method of the 4D printed bionic soft robot driven by near-infrared light for underwater operations in this application uses ink direct writing 3D printing, which is efficient and simple, and has strong structural designability.

[0029] 4. The preparation method of the 4D printing bionic soft robot driven by near-infrared light for underwater operations in this application combines 3D printing with post-polymerization chemical reduction. The prepared material has better photothermal conversion effect and good photothermal stability. The prepared soft robot has a large deformation ability and a faster reaction speed.

[0030] 5. The preparation method of the 4D printing bionic soft robot driven by near-infrared light for underwater operations in this application is simple, the raw materials are easy to obtain, the cost is low, and it has good application prospects. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of the preparation process of the 4D printing bionic soft robot in some embodiments;

[0032] Figure 2 It is the 3D printing model structure adopted by the bionic soft robot in some embodiments;

[0033] Figure 3 It is a comparison chart of the photothermal curves of the bionic soft robot based on PNH prepared in Comparative Example 2, the bionic soft robot based on GO-PNH prepared in Comparative Example 1, and the 4D printing bionic soft robot based on rGO-PNH prepared in Example 1 (under the same near-infrared light irradiation intensity of 1.5 W·cm -2 , the temperatures of PNH, GO-PNH, and rGO-PNH increased by 12.5, 32.8, and 42.0 °C respectively within 30 seconds);

[0034] Figure 4 It is the photothermal conversion performance curve of the 4D printing bionic soft robot based on rGO-PNH prepared in Example 1 under 15 times of near-infrared light on and off;

[0035] Figure 5 It is the scanning electron microscope (SEM) pictures of the 4D printing bionic soft robot based on rGO-PNH prepared in Example 1 at different magnifications;

[0036] Figure 6 It is the surface temperature change diagram of the 4D printing bionic soft robot based on rGO-PNH prepared in Example 1 under the irradiation intensity of 1.8 W cm -2 ;

[0037] Figure 7 It is a physical photo of the 4D printing bionic soft robot based on rGO-PNH prepared in Example 1 quickly responding to achieve a grasping action under near-infrared light drive;

[0038] Figure 8It is the state diagram of the 4D printing bionic soft robot based on rGO-PNH prepared in Example 1 at different stages during underwater operation driven by near-infrared light;

[0039] Figure 9 It is the morphological change diagram of the bionic soft robot based on polyaniline-poly(N-isopropylacrylamide) prepared in Comparative Example 5 under the drive of near-infrared light. Specific embodiments

[0040] The present invention will be further described in detail below through specific embodiments. It should be clear that the purpose of these embodiments is only to explain the present invention, rather than to limit the scope of the present invention. In addition, after reading the description of the present invention in detail, those skilled in the art can make various changes and modifications to the present invention as needed, and these equivalent changes are also included within the scope of the claims of this application.

[0041] Example 1: Preparation of a 4D printing bionic soft robot based on rGO-PNH

[0042] A 4D printing bionic soft robot driven by near-infrared light for underwater operation. The 4D printing bionic soft robot takes a starfish as a reference structure and is custom-designed into a starfish-like structure by 3D printing, and can simulate the starfish's predation process to quickly respond and realize the grasping / releasing of underwater objects under the drive of near-infrared light. The schematic diagram of the preparation process of the 4D printing bionic soft robot refers to Figure 1 and includes the following steps:

[0043] (1) Weigh 15 mg of graphene oxide and add it to 3 mL of deionized water, and ultrasonically disperse it evenly to obtain a graphene oxide dispersion;

[0044] (2) Add 4.5 mmol of N-isopropylacrylamide monomer, 0.015 mmol of N,N'-methylenebisacrylamide, and 0.076 mmol of lithium phenyl(2,4,6-trimethylbenzoyl)phosphate to the graphene oxide dispersion obtained in step (1), and ultrasonically disperse it evenly to obtain a graphene oxide / N-isopropylacrylamide dispersion;

[0045] (3) Weigh 0.27 g of lithium bentonite and add it to the graphene oxide / N-isopropylacrylamide dispersion obtained in step (2) to obtain an ink, and quickly stir it until the ink does not flow when inverted to obtain a GO-NIPAM ink that can be used for 3D printing;

[0046] (4) Load the GO-NIPAM ink obtained in step (3) into a cartridge with a total capacity of 5 mL and load it onto a commercial 3D printer for 3D printing, where the 3D printing model is as shown in Figure 2The shown structure is imitating a starfish structure. The size of the 3D printed model is set such that the distance from the center of the starfish to the tip of the sharp corner is L = 5 mm, and the number of printed layers is set to 2 layers, obtaining a GO-NIPAM ink with a starfish-like structure;

[0047] (5) The printed GO-NIPAM ink with a starfish-like structure in step (4) is cured with ultraviolet light for 140 s to obtain a GO-PNH hydrogel;

[0048] (6) The GO-PNH hydrogel obtained in step (5) is soaked in a 0.2 M hydrazine hydrate aqueous solution for 12 h to obtain an rGO-PNH hydrogel;

[0049] (7) The rGO-PNH hydrogel obtained in step (6) is soaked in deionized water for 12 h to remove impurities, and thus a 4D printed bionic soft robot based on rGO-PNH can be obtained.

[0050] A near-infrared light generator is used to irradiate the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 to test its photothermal curve, and the results are as Figure 3 shown. Under a near-infrared light irradiation intensity of 1.5 W·cm -2 , the temperature of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 increased by 42.0 °C within 30 s, proving that the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 has a high photothermal conversion efficiency; this also provides conditions for its high sensitivity and response speed in moving under near-infrared light driving.

[0051] The photothermal conversion performance curve of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 was tested under 15 on-off cycles of near-infrared light. The specific method is as follows: The excitation current of the near-infrared generator is adjusted to 8 A, and the distance from the rGO-PNH is 25 cm, where the water surface height is about 3 cm. When irradiating the rGO-PNH, the near-infrared light source is switched on and off 15 times, and a thermocouple is used to record the surface temperature change. The results are as Figure 4 shown. When the surface of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 is irradiated with near-infrared light, no attenuation of the photothermal conversion performance of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 is observed in the 15-cycle test, proving that the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 has good photothermal conversion stability.

[0052] The scanning electron microscope (SEM) image of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 is as Figure 5As shown, there are a large number of pores inside the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1. The pores can be used to store water and serve as channels for water absorption and loss.

[0053] Figure 6 is the graph of the surface temperature change of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 with the irradiation time under an irradiation intensity of 1.8 W·cm -2 It proves that the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 has excellent heating performance: within 5 s, it can be heated from room temperature (20.9 °C) to 32.1 °C; within 15 s, it can be heated from room temperature (20.9 °C) to 54.1 °C; within 25 s, it can be heated from room temperature (20.9 °C) to 66.1 °C; within 35 s, it can be heated from room temperature (20.9 °C) to 72.3 °C; within 45 s, it can be heated from room temperature (20.9 °C) to 74.3 °C.

[0054] The 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 can quickly respond under near-infrared light drive to achieve the grasping / releasing of underwater objects, and its action principle is as follows:

[0055] When near-infrared light irradiates one side "claw surface" of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1, the temperature of the side "claw surface" of the 4D printed bionic soft robot based on rGO-PNH close to the near-infrared light rises rapidly, and there is a temperature gradient in the thickness direction of the 4D printed bionic soft robot based on rGO-PNH. The temperature-sensitive property of PNH makes the "claw" of the 4D printed bionic soft robot based on rGO-PNH bend and tighten towards the near-infrared light side, thus achieving the grasping action;

[0056] When the near-infrared light irradiation of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 is stopped for a period of time to make the temperatures of the two side "claw surfaces" of the 4D printed bionic soft robot based on rGO-PNH tend to be equal, the temperature-sensitive property of PNH makes the "claw surface" of the 4D printed bionic soft robot based on rGO-PNH flatten, thus achieving the releasing action.

[0057] The physical photo of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 achieving the grasping action quickly under the drive of near-infrared light with an 8A excitation current and irradiated from the bottom at a distance of about 20 cm in water is as Figure 7 shown. It proves that the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 has high sensitivity and response speed in the action under near-infrared light drive.

[0058] The 4D-printed bionic soft robot based on rGO-PNH prepared in Example 1 was adhered to a thin iron wire by glue and used for underwater operations under near-infrared light driving. Its underwater operation process is as Figure 8 shown, and the specific operations are as follows:

[0059] (1) Approach: Use a thin iron wire to control the 4D-printed bionic soft robot based on rGO-PNH to approach the copper wire in water;

[0060] (2) Grasp: Turn on the near-infrared light source. Due to water loss caused by temperature rise, the 4D-printed bionic soft robot based on rGO-PNH undergoes mechanical movement, simulating the predation process of a starfish to grasp the copper wire;

[0061] (3) Lift: After grasping is completed, lifting the thin iron wire can transport the copper wire above the water surface;

[0062] (4) Release: Turn off the near-infrared light source, place the 4D-printed bionic soft robot based on rGO-PNH that has grasped the copper wire in water, and release the copper wire due to water absorption and swelling;

[0063] The results show that the 4D-printed bionic soft robot based on rGO-PNH prepared in Example 1 can successfully complete the action of precisely grasping a copper wire with a mass of 15 mg within 15 s under the drive of near-infrared irradiation; after turning off the near-infrared light source and placing the 4D-printed bionic soft robot based on rGO-PNH in water, it can complete the precise release action within a response time of 5 s.

[0064] The recycling performance of the 4D-printed bionic soft robot based on rGO-PNH prepared in Example 1 during underwater operations was tested. The results show that, referring to the aforementioned underwater operation process, after repeating the cycle 5 times, under the stimulation of near-infrared light, the 4D-printed bionic soft robot based on rGO-PNH prepared in Example 1 can complete the grasping and releasing actions repeatedly 5 times, and can still successfully grasp a copper wire with a mass of 15 mg, proving that its grasping force and grasping accuracy have not decreased significantly.

[0065] Comparative Example 1: Preparation of a bionic soft robot based on GO-PNH

[0066] A preparation method of a bionic soft robot, referring to Example 1, the difference is only that, without hydrazine hydrate reduction, steps (6) and (7) are replaced with:

[0067] (6) Swell the GO-PNH hydrogel obtained in step (5) in deionized water to obtain a bionic soft robot based on GO-PNH.

[0068] The bionic soft robot based on GO-PNH prepared in Comparative Example 1 was irradiated with a near-infrared light generator to test its photothermal curve, and the results are as Figure 3 shown. It was found that under the near-infrared light irradiation intensity of 1.5 W·cm -2 , the temperature of the bionic soft robot based on GO-PNH prepared in Comparative Example 1 increased by 32.8 °C within 30 seconds. The temperature increase effect of the bionic soft robot based on GO-PNH prepared in Comparative Example 1 under the same condition of near-infrared light irradiation was much worse than that of the 4D printed bionic soft robot based on rGO-PNH prepared in Example 1 after reduction with hydrazine hydrate.

[0069] Comparative Example 2: Preparation of a bionic soft robot based on PNH

[0070] A preparation method of a bionic soft robot, referring to Comparative Example 1, the difference is only that graphene oxide is not added in step (1); a bionic soft robot based on PNH was prepared.

[0071] The bionic soft robot based on PNH prepared in Comparative Example 2 was irradiated with a near-infrared light generator to test its photothermal curve, and the results are as Figure 3 shown. It was found that under the near-infrared light irradiation intensity of 1.5 W·cm -2 , the temperature of the bionic soft robot based on PNH prepared in Comparative Example 2 only increased by 12.5 °C within 30 seconds. The heating rate of the bionic soft robot based on PNH in Comparative Example 2 was much worse than that of the bionic soft robot based on GO-PNH prepared in Comparative Example 1 and the 4D printed bionic soft robot based on rGO-PNH in Example 1.

[0072] Comparative Example 3: Preparation of rGO first and then synthesis of rGO-PNH hydrogel

[0073] Referring to Example 1, the difference is only that rGO is prepared first and then rGO-PNH hydrogel is synthesized. The specific steps are as follows:

[0074] (1) Weigh 15 mg of graphene oxide, soak it in 0.2 M hydrazine hydrate aqueous solution for 12 h, and wash it with water to obtain reduced graphene oxide;

[0075] (2) Add the reduced graphene oxide (rGO) obtained in step (1) to 3 mL of deionized water, and disperse it evenly by ultrasonic treatment to obtain a reduced graphene oxide dispersion;

[0076] (3) adding 4.5 mmol of N-isopropylacrylamide monomer, 0.015 mmol of N,N'-methylenebisacrylamide and 0.076 mmol of phenyl (2,4,6-trimethylbenzoyl) phosphate lithium salt to the reduced graphene oxide dispersion obtained in step (1), and uniformly dispersing by ultrasonication to obtain a reduced graphene oxide / N-isopropylacrylamide dispersion;

[0077] (4) Weighing 0.27 g of lithium bentonite, adding it to the reduced graphene oxide / N-isopropylacrylamide dispersion obtained in step (3) to obtain ink, and rapidly stirring until the ink is inverted and does not flow, to obtain reduced graphene oxide-NIPAM ink that can be used for 3D printing;

[0078] (5) The reduced graphene oxide-NIPAM ink obtained in step (4) is loaded into a 5 mL barrel and loaded onto a commercial 3D printer for 3D printing, wherein the 3D printed model is a starfish-like structure, the size of the 3D printed model is a distance from the center of the starfish to the top of the sharp corner is L=5 mm, and the number of printing layers is set to 2 layers, thereby obtaining a starfish-like rGO-NIPAM ink;

[0079] (6) The rGO-NIPAM ink with the starfish-like structure printed in step (5) is cured with UV light in an attempt to obtain rGO-PNH hydrogel; at this time, experimental studies have found that it is impossible to obtain a PNIPAM network, even if the UV curing conditions are adjusted. This also shows that the method of first preparing rGO and then synthesizing rGO-PNH hydrogel cannot successfully produce a hydrogel system. Only by first synthesizing GO-PNH hydrogel according to the method of Example 1 and then reducing it to obtain rGO-PNH hydrogel can a hydrogel system be successfully prepared; at the same time, it can ensure that the prepared 4D printed bionic soft robot has a certain degree of opacity, so that under near-infrared light irradiation, the 4D printed bionic soft robot based on rGO-PNH has a temperature gradient in the thickness direction, thereby achieving a grasping or releasing action.

[0080] Comparative Example 4: Using other photothermal conversion materials

[0081] Referring to Example 1, the only difference is that graphene oxide is replaced with other light-to-heat conversion materials (such as macerated nanosheets), and the specific steps are as follows:

[0082] (1) Weighing 15 mg of macau nanosheets, adding them into 3 mL of deionized water, and dispersing them evenly by ultrasonication to obtain a macau nanosheet dispersion;

[0083] (2) adding 4.5 mmol of N-isopropylacrylamide monomer, 0.015 mmol of N,N'-methylenebisacrylamide and 0.076 mmol of phenyl (2,4,6-trimethylbenzoyl) phosphate lithium salt to the macene dispersion obtained in step (1), and uniformly dispersing by ultrasonication to obtain a macene / N-isopropylacrylamide dispersion;

[0084] (3) Weighing 0.27 g of hectorite, adding it to the macerate / N-isopropylacrylamide dispersion obtained in step (2) to obtain ink, and rapidly stirring until the ink stands upside down and does not flow, thereby obtaining macerate-NIPAM ink that can be used for 3D printing;

[0085] (4) The mecanin-NIPAM ink obtained in step (3) is loaded into a 5 mL barrel and loaded onto a commercial 3D printer for 3D printing, wherein the 3D printed model is a starfish-like structure, the size of the 3D printed model is set such that the distance from the center of the starfish to the top of the sharp corner is L=5 mm, and the number of printing layers is set to 2 layers, thereby obtaining a starfish-like structure of mecanin-NIPAM ink;

[0086] (5) The starfish-like structured mcphene-NIPAM ink printed in step (4) was cured by ultraviolet light for 140 seconds to try to obtain a mcphene-PNH hydrogel; at this time, experimental studies have found that it is impossible to obtain a PNIPAM network, even if the ultraviolet light curing conditions are adjusted. This also proves that the method based on the present invention, using graphene oxide as a photothermal conversion material, overcomes the technical difficulty of not being able to obtain a PNIPAM network compared to using other photothermal conversion materials (such as mcphene nanosheets).

[0087] Comparative Example 5:

[0088] (1) Without adding graphene oxide, 4.5 mmol of N-isopropylacrylamide monomer, 0.015 mmol of N,N'-methylenebisacrylamide and 0.076 mmol of phenyl (2,4,6-trimethylbenzoyl) phosphate lithium salt were added to 3 mL of deionized water, and then ultrasonically accelerated the dissolution;

[0089] (2) Weigh 0.27 g of lithium bentonite and add it to the solution obtained in step (1), and stir it rapidly until the ink stands upside down and does not flow, thereby obtaining N-isopropyl acrylamide ink that can be used for 3D printing.

[0090] (3) Load the N-isopropylacrylamide ink obtained in step (2) into a cartridge with a total capacity of 5 mL and load it onto a commercial 3D printer for 3D printing. The 3D printing model has a starfish-like structure. The size of the 3D printing model is such that the distance from the center of the starfish to the tip of the sharp corner is L = 5 mm. The number of printing layers is set to 2 layers to obtain an N-isopropylacrylamide ink with a starfish-like structure.

[0091] (4) Cure the printed N-isopropylacrylamide ink with a starfish-like structure in step (3) using ultraviolet light for 140 s to obtain a hydrogel, and swell it in deionized water to obtain a PNH hydrogel.

[0092] (5) Prepare 45 mL of 1 M hydrochloric acid aqueous solution, add 0.58 mL of aniline, mix well, and refrigerate at 4 °C until reaching a constant temperature.

[0093] (6) Ultrasonically dissolve 1.45 g of ammonium persulfate solution in 5 mL of aqueous solution and refrigerate at 4 °C until reaching a constant temperature.

[0094] (7) Immerse the PNH hydrogel obtained in step (4) in the solution obtained in step (5) at 4 °C for 12 h, and then add the solution obtained in step (6) to initiate the polymerization of aniline at 4 °C for 12 h to form a polyaniline network.

[0095] (8) Immerse the polyaniline-poly(N-isopropylacrylamide) hydrogel obtained in step (7) in deionized water to remove impurities to obtain a bionic soft robot based on polyaniline-poly(N-isopropylacrylamide).

[0096] The bionic soft robot based on polyaniline-poly(N-isopropylacrylamide) prepared in Comparative Example 5 has a photocurrent of 8 A under near-infrared light excitation. The height from the bionic soft robot based on polyaniline-poly(N-isopropylacrylamide) prepared in Comparative Example 5 is 25 cm, where the water surface height is about 3 cm. The photos of the morphological changes after irradiation for 20 s are as Figure 9 shown. By comparing with Example 1, it can be found that the bionic soft robot based on polyaniline-poly(N-isopropylacrylamide) prepared in Comparative Example 5 has poor deformation ability. This shows that for bionic soft robots, the selection of the photothermal conversion material will affect the deformation ability of the bionic soft robot, thereby affecting the grasping effect (grasping force and grasping accuracy).

[0097] The above-provided embodiments are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit their execution order. Obvious improvements made by those skilled in the art in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A preparation method of a 4D printing bionic soft robot driven by near-infrared light for underwater operations, characterized in that, It includes the following steps: (1) Add graphene oxide into water and perform ultrasonic treatment to obtain a graphene oxide dispersion; (2) Add N-isopropylacrylamide monomer, N,N'-methylenebisacrylamide, and lithium phenyl(2,4,6-trimethylbenzoyl)phosphate into the graphene oxide dispersion obtained in step (1), and perform ultrasonic treatment to obtain a GO-NIPAM dispersion; in the GO-NIPAM dispersion, the dosage ratio of graphene oxide:N-isopropylacrylamide monomer:N,N'-methylenebisacrylamide:lithium phenyl(2,4,6-trimethylbenzoyl)phosphate is 15 mg:(4 - 5) mmol:(0.013 - 0.017) mmol:(0.074 - 0.078) mmol; (3) Add bentonite lithium to the GO-NIPAM dispersion obtained in step (2) to obtain an ink; quickly stir until the ink does not flow when inverted to obtain a GO-NIPAM ink that can be used for 3D printing; wherein, the dosage of bentonite lithium is 0.08 to 0.1 g·mL -1 ; (4) Load the GO-NIPAM ink obtained in step (3) into a cartridge and perform 3D printing, where the 3D printing model has a starfish-like structure to obtain a starfish-like GO-NIPAM ink; (5) Cure the printed starfish-like GO-NIPAM ink in step (4) using ultraviolet light to obtain a GO-PNH hydrogel; (6) Immerse the GO-PNH hydrogel obtained in step (5) in a 0.1 - 0.3 M hydrazine hydrate aqueous solution to obtain an rGO-PNH hydrogel; (7) Immerse the rGO-PNH hydrogel obtained in step (6) in deionized water to remove impurities, and then a 4D printing bionic soft robot based on rGO-PNH can be obtained.

2. The preparation method according to claim 1, characterized in that, In step (2), in the graphene oxide / N-isopropylacrylamide dispersion, the dosage ratio of graphene oxide:N-isopropylacrylamide monomer:N,N'-methylenebisacrylamide:lithium phenyl(2,4,6-trimethylbenzoyl)phosphate is 15 mg:4.5 mmol:0.015 mmol:0.076 mmol.

3. The preparation method according to claim 1, characterized in that, In step (3), the dosage of bentonite is 0.09 g·mL -1 .

4. The preparation method according to claim 1, characterized in that, In step (3), the mass ratio of lithium bentonite to graphene oxide is 18:

1.

5. The preparation method according to claim 1, characterized in that, In step (1), in the graphene oxide dispersion, the ratio of graphene oxide to water is 5 g:1 L.

6. The preparation method according to claim 1, characterized in that, In step (6), the concentration of the hydrazine hydrate aqueous solution is 0.2 M, and the immersion time in the hydrazine hydrate aqueous solution is 12 h.

7. The preparation method according to claim 1, characterized in that, In step (5), the ultraviolet light curing time is 100 - 180 s.

8. The preparation method according to claim 7, characterized in that, In step (5), the ultraviolet light curing time is 140 s.

9. A 4D printing bionic soft robot driven by near-infrared light for underwater operations prepared by the preparation method according to claims 1 to 8.

10. The application of the 4D printing bionic soft robot driven by near-infrared light for underwater operations according to claim 9 in underwater operations, characterized in that, It includes the following steps: Fix the 4D printing bionic soft robot for underwater operation driven by near-infrared light described in claim 9 on a rod to control the orientation of the 4D printing bionic soft robot; irradiate one side of the 4D printing bionic soft robot with near-infrared light to enable the 4D printing bionic soft robot to complete a grasping action.

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