High-sensitivity humidity-responsive film and application thereof in preparation of mobile soft robot

Abstract

The application discloses a high-sensitivity humidity response type film and application thereof in preparation of a mobile soft robot, and belongs to the technical field of flexible driver materials, and a preparation method comprises the following steps: (1) uniformly mixing Nafion solution and N,N-dimethylacetamide, then adding aniline black, fully stirring, and performing vacuumizing treatment to obtain a Nafion-aniline black solution; then, the vacuumized Nafion-aniline black solution is dropped on a glass sheet and heated, the Nafion-aniline black film is peeled off from the glass sheet after drying, and the Nafion-aniline black film is obtained. The application proposes a new use of the Nafion-aniline black material, specifically, the application of the Nafion-aniline black material in preparation of a humidity response driver, a finger non-contact guiding rolling robot or a Mobius ring robot. The prepared soft robot can be controlled by the finger non-contact to move forward and backward or even curve, and the soft robot can also move continuously under continuous humidity input. Moreover, the preparation process is simple, the flow is short, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of flexible actuator materials technology, specifically to a highly sensitive humidity-responsive thin film and its application in the fabrication of mobile soft robots. Background Technology

[0002] Flexible smart materials can convert external stimuli into mechanical energy, which can be directly utilized in their own deformation and movement. Utilizing energy from the environment, soft actuators made from flexible smart materials can achieve movements such as bending, winding, and even bouncing. Thanks to their simple actuation structure, high degree of freedom, and strong environmental adaptability, they are increasingly becoming a very important research direction in the field of soft robotics.

[0003] In recent years, researchers have made significant progress in areas such as high sensitivity, large deformation, and robustness. However, effectively utilizing humidity, a relatively weak and difficult-to-control stimulus compared to light, heat, and magnetism, remains a major challenge. Although a considerable number of humidity actuators have been published, there is still significant room for improvement, particularly in terms of actuation speed and controllability. In particular, there is an urgent need to develop soft robots capable of generating periodic motion based on their own structure without periodic energy input. The proposed work will undoubtedly contribute to the practical application of flexible smart materials.

[0004] Chinese patent application CN118623833A discloses a method and application for preparing a programmable humidity actuator using an ink marker coating. Specifically, an MXene dispersion is filtered to obtain an MXene film. Then, an oil-based ink is uniformly coated onto one side of the MXene film using a commercially available oil-based marker, resulting in an MXene-oil-based ink bilayer humidity actuator. This actuator utilizes the interaction between the oxygen-containing groups in the highly hydrophilic MXene material and water molecules, causing expansion, while the oil-based ink side does not interact with water molecules, thus creating a volume mismatch between the two layers, causing the entire film to bend towards the ink side. Based on this, the pure MXene film is cut using a laser, and oil-based ink is coated at designated locations to obtain a programmable humidity actuator. That is, the bending only occurs in the ink-coated bilayer region. However, this patent does not involve Nafion-aniline black material, nor does it relate to applications in mobile robots.

[0005] Chinese patent application CN117429103A discloses a light-driven thin film utilizing photoresponsive deformation and its application in biomimetic actuators and photoelectric conversion triboelectric nanogenerators. Specifically, a Nafion polymer film mixed with black pigment can generate a photothermal conversion effect under light, while the PE film bonded to the other side generates thermal expansion. The volume mismatch caused by the expansion on both sides induces bending towards the Nafion-black pigment side under light. Based on this, various functional light actuators can be developed by utilizing the anisotropic mechanical properties of PE. Although the patent mentions Nafion-aniline black material, it is only used in the fields of light-driven films and photoelectric conversion triboelectric nanogenerators, and not in the field of humidity-responsive actuators. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to propose a new use for Nafion-aniline black material.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] The first aspect of the present invention proposes the application of Nafion-aniline black films in the preparation of humidity-responsive actuators, finger-guided non-contact rolling robots, or Möbius ring robots.

[0009] Preferably, the method for preparing the Nafion-aniline black film includes the following steps:

[0010] (1) Preparation of Nafion-aniline black solution: After mixing Nafion solution with N,N-dimethylacetamide (DMAC) evenly, add aniline black, stir thoroughly, and then perform vacuum treatment to obtain Nafion-aniline black solution;

[0011] The mass ratio of Nafion solution, N,N-dimethylacetamide (DMAC), and aniline black is 9:3:0.1;

[0012] (2) Preparation of Nafion-aniline black film: The vacuum-sealed Nafion-aniline black solution is dropped onto a glass slide and heated. After drying, the Nafion-aniline black film is peeled off from the glass slide to obtain the film. The thickness of the Nafion-aniline black film is 20-28 μm.

[0013] Preferably, in step (1), a vortex mixer is used to mix the mixture evenly for 3-5 hours, and more preferably 4 hours.

[0014] Preferably, the vacuuming time in step (1) is 20-40 min, and more preferably, it is 30 min.

[0015] Preferably, the heating temperature in step (2) is 40-60℃ and the heating time is 2-4h. More preferably, it is 50℃ and 3h.

[0016] Preferably, the thickness of the Nafion-aniline black film in step (2) is 23 μm.

[0017] A second aspect of the present invention provides a finger-guided rolling robot, which is obtained by cutting the above-mentioned Nafion-aniline black film into a rectangular film and then connecting the end ends together; the finger-guided rolling robot can roll when the finger approaches.

[0018] Preferably, the Nafion-aniline black film is cut into (50-60)×(8-15)mm pieces, and the first and last ends are bonded together with PP tape, with the bonded portion being (3-5)×(8-15)mm.

[0019] The third aspect of the present invention provides a Möbius ring robot, which is obtained by cutting the above-mentioned Nafion-aniline black film into a rectangular film, twisting the rectangular film by 180°, and then connecting the end ends together; the Möbius ring robot can perform continuous ring motion in a humidity environment with vertical upward transmission.

[0020] Preferably, the Nafion-aniline black film is cut into (60-70)×(3-5)mm pieces, and the ends are bonded together with PP tape, with the bonded portion being (2-4)×(3-5)mm.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention proposes a novel application for Nafion-aniline black material, specifically its use in the fabrication of humidity-responsive actuators, finger-guided non-contact rolling robots, or Möbius loop robots. Due to the strong attraction of water by the anionic groups within the Nafion-aniline black film, which can form hydrogen bonds with water, it exhibits a strong attraction for moisture. Simultaneously, thanks to the film's porous structure, it possesses strong water storage and diffusion capabilities. Therefore, under a certain humidity gradient, the film can locally undergo rapid humidity expansion, causing it to bend towards the side with lower humidity. When removed from the high-humidity environment, the film quickly returns to its shape. Due to its monolayer nature, both sides of the film can respond to humidity gradients, achieving rapid humidity response and offering advantages such as fast actuation speed and simple structure.

[0023] 2. This invention fabricates a humidity actuator with ultra-high humidity sensitivity and a highly controllable mobile robot capable of forward and backward movement and even zigzag motion through non-contact manipulation. It also includes a self-contained mobile robot operating under continuous humidity input. Furthermore, the fabrication process is simple, short, and low-cost.

[0024] 3. For finger-guided non-contact rolling robots, due to the effect of the ring-shaped adhesive, the local bending of the Nafion-aniline black film transforms into a convex effect towards the humidity direction. Therefore, during deformation, the center of gravity of the ring robot shifts forward in the direction of humidity, causing it to roll. The finger can provide the local humidity gradient stimulation required by the ring robot, thus guiding its movement.

[0025] 4. For the Möbius ring robot, due to the design of the Möbius ring, the humidity bending of the Nafion-aniline black film will be converted into its own rotation, thereby interacting with the ground and driving itself to generate ring motion. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation of Nafion-aniline black film in Example 1 of the present invention.

[0027] Figure 2 This is a cross-sectional scanning electron microscope image of the Nafion-aniline black film in Example 1 of the present invention.

[0028] Figure 3 This is a performance test diagram of the humidity response driver in Embodiment 1 of the present invention.

[0029] Figure 4 This is a schematic diagram of the finger-guided rolling robot in Embodiment 1 of the present invention.

[0030] Figure 5 This is an optical photograph of the finger-guided rolling robot in Embodiment 1 of the present invention.

[0031] Figure 6 This is a schematic diagram of the Möbius ring robot in Embodiment 1 of the present invention, where A is a schematic diagram of the motion principle and B is a schematic diagram of the motion trajectory.

[0032] Figure 7 This is an optical photograph of the Möbius ring robot in Embodiment 1 of the present invention.

[0033] Figure 8 This is a stretching curve of films with different aniline black contents in Example 2 of the present invention.

[0034] Figure 9 This is a performance test curve of the humidity driver with different aniline black contents in Example 3 of the present invention.

[0035] Figure 10 The graphs show the performance tests of films with different DMAC solutions or film thicknesses in Example 4 of this invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0038] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0039] This invention specifically describes the preparation process of Nafion and aniline black (water-soluble) materials. Other Nafion materials prepared using this invention should also be within the scope of protection. This invention specifically uses a D520 membrane solution manufactured by DuPont as the substrate membrane. Other existing substrate membranes, such as Flemion membranes from Asahi Glass, Aciplex membranes from Asahi Chemical, or Aquivion membranes from Solvay Solexis, should also be within the scope of protection.

[0040] Example 1:

[0041] The method for preparing Nafion-aniline black thin films includes the following steps:

[0042] (1) Preparation of Nafion-aniline black solution: 4.5g Nafion, 1.5g DMAC solution and 0.05g aniline black (water-soluble) dye powder were mixed and stirred in a vortex mixer for 4h. Then, after vacuum treatment for 30min, a Nafion-aniline black solution with a mass fraction of 0.8% aniline black was obtained.

[0043] (2) Preparation of Nafion-aniline black film: Using a pipette, 2 mL of the prepared Nafion-aniline black solution was dropped onto a 75×25 mm glass slide, and then heated at 50°C for 3 hours using a heating platform. The glass slide with the Nafion-aniline black film was placed in deionized water, and after 5 seconds, the film detached from the glass slide. The film was then transferred from the water to filter paper using the glass slide. After removing the water, a 2 mm wide area at the edge was cut off to obtain the Nafion-aniline black film. (A schematic diagram of the preparation process is shown below.) Figure 1 The diagram illustrates the process of preparing this Nafion-aniline black film, from solution to drop casting and drying into a film.

[0044] The cross-sectional image of the prepared Nafion-aniline black film, magnified by scanning electron microscopy, is shown below. Figure 2 As shown, its thickness is approximately 23 μm, and it contains a porous structure that facilitates moisture absorption and diffusion, promoting its rapid response to humidity.

[0045] The Nafion-aniline black film prepared in this embodiment can be used to fabricate humidity-responsive actuators, finger-guided non-contact rolling robots, or Möbius ring robots.

[0046] Preparation of Nafion-aniline black humidity-responsive actuator: Cut the dried Nafion-aniline black film into a 30×10mm rectangular film, attach one end to the glass substrate with utility tape, and leave a 20×10mm free end.

[0047] Set up a humidity-driven test platform: Use a heating platform to heat water to provide a humidity gradient environment. Cover it with a stainless steel mesh (400 mesh) to support the glass substrate and the actuator connected to it. The height of the mesh from the liquid surface is 10mm.

[0048] The humidity-responsive driver was used to test the bending angle and bending speed. The test results are as follows: Figure 3 As shown in the figure, "△RH" represents the relative humidity difference, which is the surface humidity of the stainless steel mesh minus the air humidity. The humidity actuator can generate a bending angle of over 180° when the relative humidity difference is 40%, and also has an extremely fast deformation speed of 205° / s.

[0049] Preparation of a finger-guided circular rolling robot: Dry Nafion-aniline black film is cut into rectangular films of 55×10mm, and the first and last ends are glued together with PP tape. The glued part is 4×10mm.

[0050] Rolling tests were conducted on the fabricated finger-guided circular rolling robot: The finger was placed 5mm above and diagonally above the soft robot, causing it to bend and bulge towards the finger while the finger slowly moved forward. Rolling occurred when the center of gravity shifted sufficiently to induce rolling. Repeating this process allowed the soft robot to continuously roll towards the finger. Figure 4 As shown, when a finger approaches this rolling robot, the moisture from the finger acts on the local surface of the soft robot, transferring moisture from the finger to the local surface and diffusing inwards. This causes varying degrees of moisture expansion in the normal cross-section, resulting in a bulge bending towards the finger. As the degree of bending increases, the center of gravity of the entire ring shifts. When the shift is large enough, the soft robot will roll. Repeating this process allows the soft robot to continuously roll towards the finger.

[0051] Optical photographs of a finger-guided rolling robot performing straight-line and ramp rolling, as shown below. Figure 5 As shown in the figure, guided by a finger, the soft robot rolls towards the finger at a speed of approximately 5 mm / s. This soft robot can also perform non-contact rolling guided by a finger on surfaces with certain obstacles and slopes.

[0052] Preparation of the Möbius ring self-continuous motion robot: Cut the dried Nafion-aniline black film into a rectangular film of 65×3mm, twist it 180°, and then stick the first and second ends together with PP tape. The sticking part is 3×4mm.

[0053] Construct a humidity-driven testing platform: Use a heating platform to heat water to provide a humidity gradient environment. Cover the platform with a stainless steel mesh (400 mesh) to support the film, with the mesh 10mm above the liquid surface. Place the film on the stainless steel mesh and heat the water to 38℃.

[0054] A schematic diagram of the Möbius ring robot is shown below. Figure 6 As shown in the figure, the Möbius ring robot, in a vertically upward humidity environment, can generate interaction forces by continuously rotating and contacting the ground, thus propelling itself into a ring motion.

[0055] Optical photographs of the Möbius ring robot moving on a stainless steel mesh, such as Figure 7 As shown in the figure, the Möbius ring robot continuously generates ring-shaped displacements under humidity stimulation. The white curve represents its motion trajectory.

[0056] Comparative Example 1:

[0057] A Nafion humidity-driven thin film preparation method was described, which differs from Example 1 in that aniline black was not added. Otherwise, the process is the same as in Example 1.

[0058] Comparative Example 2:

[0059] The difference between this comparative example and Example 1 is that in step (1), the amount of aniline black is 0.025 g, resulting in a Nafion-aniline black solution with a mass fraction of 0.4%. The rest is the same as in Example 1.

[0060] Comparative Example 3:

[0061] The difference between this comparative example and Example 1 is that in step (1), the amount of aniline black is 0.075 g, resulting in a Nafion-aniline black solution with a mass fraction of 1.2% aniline black. The rest is the same as in Example 1.

[0062] Comparative Example 4:

[0063] The difference between this comparative example and Example 1 is that the mass of the DMAC solution is 0.8g, while the rest is the same as in Example 1.

[0064] Comparative Example 5:

[0065] The difference between this comparative example and Example 1 is that the mass of the DMAC solution is 3g, while the rest is the same as in Example 1.

[0066] Comparative Example 6:

[0067] The difference between this comparative example and Example 1 is that the thickness of the Nafion-aniline black film is 17 μm, while the rest is the same as in Example 1.

[0068] Comparative Example 7:

[0069] The difference between this comparative example and Example 1 is that the thickness of the Nafion-aniline black film is 35 μm, while the rest is the same as in Example 1.

[0070] Example 2:

[0071] Tensile mechanical properties were tested on 30×10⁻⁶ samples of the films prepared in Example 1 and Comparative Examples 1-3. The test results are shown below. Figure 8 .

[0072] Wherein Nafion is the Nafion humidity-driven film prepared in Comparative Example 1, AB-Nafion 0.8 is the AB-Nafion film sample prepared in Example 1, AB-Nafion 0.4 is the AB-Nafion film sample prepared in Comparative Example 2, and AB-Nafion 1.2 is the AB-Nafion film sample prepared in Comparative Example 3.

[0073] pass Figure 8 Analysis of the test results showed that the brittleness of the humidity-driven films increased after the addition of aniline black solution. Furthermore, the elastic modulus of Comparative Examples 2 and 3 decreased compared to the Nafion humidity actuator of Comparative Example 1 (without aniline black), and the Nafion-aniline black film in Comparative Example 3 became more brittle, making it difficult to fabricate into a mobile robot.

[0074] Example 3:

[0075] The humidity actuators prepared in Example 1 and Comparative Examples 1-3 were subjected to humidity-driven bending performance tests. The test results are shown below. Figure 9 .

[0076] pass Figure 9 Performance testing and analysis showed that the Nafion-aniline black film prepared in Comparative Example 3, due to its higher aniline black content and lower elastic modulus, exhibited the fastest driving speed and the largest humidity driving angle. The actuator obtained in Example 1 performed second best. The films prepared in Comparative Examples 3 and 1 showed the worst performance.

[0077] Example 4:

[0078] The films prepared in Example 1 and Comparative Examples 4-7 were subjected to performance tests, and the results were compared with those of Example 1. Figure 10 As shown in the figure, it can be seen that the samples of Comparative Example 4 and Comparative Example 6 were difficult to form films and broke upon peeling from the glass substrate, making them unsuitable for application and testing. In contrast, Comparative Example 5 and Comparative Example 7 were able to peel from the glass substrate to form complete films.

[0079] However, by conducting the same humidity performance tests as in Example 1 on Comparative Examples 5 and 7, under a relative humidity difference of 28%, Comparative Example 7 showed no advantage in either bending angle or bending speed. While Comparative Example 5 exhibited a greater bending angle compared to Example 1, its bending speed was significantly slower. Therefore, overall, Example 1 demonstrates superior comprehensive performance.

[0080] Example 5:

[0081] The difference between this embodiment and Embodiment 1 is that the thickness of the Nafion-aniline black film is 20 μm, while the rest is the same as in Embodiment 1.

[0082] Example 6:

[0083] The difference between this embodiment and Embodiment 1 is that the thickness of the Nafion-aniline black film is 28 μm, while the rest is the same as in Embodiment 1.

[0084] Example 7:

[0085] The difference between this embodiment and Embodiment 1 is that the vacuuming time in step (1) is 20 minutes, and the heating temperature in step (2) is 60°C and the heating time is 2 hours. The rest is the same as in Embodiment 1.

[0086] Example 8:

[0087] The difference between this embodiment and Embodiment 1 is that the vacuuming time in step (1) is 40 minutes, and the heating temperature in step (2) is 40°C and the heating time is 4 hours. The rest is the same as in Embodiment 1.

[0088] The properties of the films prepared in Examples 5-8 are similar to those in Example 1.

[0089] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The application of Nafion-aniline black thin film in the fabrication of humidity-responsive actuators, finger-guided non-contact rolling robots, or Möbius ring robots, characterized in that, The method for preparing the Nafion-aniline black film includes the following steps: (1) Preparation of Nafion-aniline black solution: Nafion solution and N,N-dimethylacetamide are mixed evenly and then aniline black dye is added. After stirring thoroughly, vacuum treatment is performed to obtain Nafion-aniline black solution; the mass ratio of Nafion solution, N,N-dimethylacetamide and aniline black is 9:3:0.

1. (2) Preparation of Nafion-aniline black film: The vacuum-sealed Nafion-aniline black solution is dropped onto a glass slide and heated. After drying, the Nafion-aniline black film is peeled off from the glass slide to obtain the film. The thickness of the Nafion-aniline black film is 20~28μm.

2. The application according to claim 1, characterized in that, In step (1), a vortex mixer is used to mix the mixture evenly for 3-5 hours.

3. The application according to claim 1, characterized in that, The vacuuming time in step (1) is 20-40 minutes.

4. The application according to claim 1, characterized in that, In step (2), the heating temperature is 40-60℃ and the heating time is 2-4h.

5. The application according to claim 4, characterized in that, In step (2), the heating temperature is 50℃ and the heating time is 3h.

6. A finger-guided non-contact rolling robot, characterized in that, It is obtained by cutting the Nafion-aniline black film in any one of claims 1-5 into a rectangular film and then connecting the two ends together; the finger-non-contact guided rolling robot can roll when the finger approaches.

7. The finger-guided non-contact rolling robot according to claim 6, characterized in that, Cut the Nafion-aniline black film into (50-60)×(8-15) mm pieces, and stick the first and last ends together with PP tape. The sticking part is (3-5)×(8-15) mm.

8. A Möbius ring robot, characterized in that, It is obtained by cutting the Nafion-aniline black film in any one of claims 1-5 into a rectangular film, twisting the rectangular film by 180°, and then connecting the two ends together; the Möbius ring robot can make continuous ring motion in a humidity environment that is transmitted vertically upward.

9. The Möbius ring robot according to claim 8, characterized in that, Cut the Nafion-aniline black film into (60-70)×(3-5) mm pieces, and stick the first and last ends together with PP tape. The sticking part is (2-4)×(3-5) mm.

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