Fabrication method of cellulose-based deformable and color-changing flexible actuator

Abstract

This invention belongs to the field of smart materials, and its purpose is to provide a method for preparing a cellulose-based deformable and color-changing flexible actuator. This method should be able to prepare a dual-response, deformable and color-changing, low-cost flexible actuator, and the preparation process should be simple and easy to implement. The technical solution is a method for preparing a cellulose-based deformable and color-changing flexible actuator, comprising the following steps: 1) Preparing a humidity-responsive cellulose nanocrystal-polyethylene glycol diacrylate film; 2) Preparing an ionic electroactive actuator based on carboxylated bacterial cellulose; 3) Preparing a cellulose-based deformable and color-changing flexible actuator.

Description

Technical Field

[0001] This invention belongs to the field of smart materials, specifically relating to a method for preparing a deformable and color-changing flexible actuator based on cellulose. Background Technology

[0002] Traditional rigid robots have limitations in compliance when interacting with the natural environment, limited to parallel or rotational movement. While offering precise motion, their adaptability is limited, making them unsuitable for complex, unstructured environments and significantly restricting their application scope. In recent years, with the expanding fields of robotics applications, specialized areas such as healthcare and biomimetic motion have placed higher demands on robot compliance. For example, in minimally invasive surgery, robots are required to remove foreign objects from patients without harming them; and the imitation of biological features needs to be more realistic and flexible. Furthermore, since some organisms can change their shape to adapt to constantly changing environments, endowing soft robots with the ability to interact with the environment and integrate more feedback is of great significance. Therefore, color-changing soft robots have attracted widespread attention both domestically and internationally. Various color-tunable soft actuators have been fabricated using materials based on chemical or structural colors, enabling shape deformation and color change, and hold promise for applications in biomimetic robots, stealth anti-counterfeiting, and military camouflage. Consequently, many scientists have begun research into fabricating color-changing soft robots from flexible or deformable materials.

[0003] Currently, the deformable and color-changing flexible actuators that have been prepared have drawbacks such as single driving stimulus, non-renewability, complex preparation process, and expensive metallic color materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the above-mentioned background technology and provide a method for preparing a flexible actuator based on cellulose that is deformable and color-changing; the method should be able to prepare a flexible actuator that is dual-response, deformable and color-changing, and low in cost, and the preparation process is simple and easy to implement.

[0005] The technical solution provided by this invention is:

[0006] The method for preparing a cellulose-based deformable and color-changing flexible actuator includes the following steps:

[0007] Step 1): Prepare a humidity-responsive color-changing cellulose nanocrystal-polyethylene glycol diacrylate film;

[0008] Step 1.1): Mix the cellulose nanocrystal solution and the polyethylene glycol diacrylate solution in a ratio of 20-25:0-0.2 parts by weight to form a mixed solution;

[0009] Step 1.2): Seal and stir the aforementioned mixed solution at room temperature for 3-4 hours;

[0010] Step 1.3): Pour the stirred mixture into a mold and dry at room temperature for 48-72 hours;

[0011] Step 1.4): Irradiate the dried cellulose film with a UV lamp for 5 minutes;

[0012] Step 1.5): After cooling at room temperature for a period of time, remove the film and cut it into small rectangular strips;

[0013] Step 2): Prepare an ion-type electroactive actuator based on carboxylated bacterial cellulose (existing technology, a high-performance flexible actuator, see CN112480457A);

[0014] Step 3): Fabricate a cellulose-based deformable and color-changing flexible actuator;

[0015] Step 3.1): Attach the rectangular strips to both sides of the ionotropic electroactive actuator based on carboxylated bacterial cellulose, and wrap it with filter paper;

[0016] Step 3.2) Place the wrapped membrane in the middle of the glass slide and press it with a clamp at room temperature for 48-72 hours;

[0017] Step 3.3) Remove the membrane after pressing and cut it into rectangular strips of 10×40mm.

[0018] The prepared driver is placed in the storage instrument for later experimental testing.

[0019] The prepared driver also needs to be tested for displacement and humidity-induced color change using an output displacement platform.

[0020] Preferably, the volume concentration of the cellulose nanocrystal solution is 1%.

[0021] Preferably, the volume concentration of the polyethylene glycol diacrylate solution is 5%.

[0022] Preferably, the mixing temperature in step 1.1) is 10–40°C.

[0023] The beneficial effects of this invention are:

[0024] 1. Cellulose nanocrystals and carboxylated bacterial cellulose have good biodegradability and low cost. Therefore, this invention uses cellulose nanocrystals and carboxylated bacterial cellulose as a matrix, which is inexpensive, readily available, and environmentally friendly.

[0025] 2. The preparation method using cellulose and clamping force provided by the present invention greatly simplifies the preparation process of deformable and color-changing flexible actuators.

[0026] 3. In this invention, polyethylene glycol diacrylate is added to a cellulose mixture, which physically crosslinks with cellulose, resulting in cellulose films with different structural colors after drying.

[0027] 3. The deformable and color-changing flexible actuator prepared by this invention can generate large deformation and displacement under a voltage drive of 2V and 100mHz, and has a fast response speed, achieving both large deformation and rapid response simultaneously. Furthermore, the surface of the actuator can change color under the stimulation of humidity changes. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the present invention (where 1A is a structural diagram; 1B is a photograph).

[0029] Figure 2 This is a schematic diagram illustrating the working principle of the present invention (where 2A is the driver in the unpowered state; 2B is the driver in the powered state).

[0030] Figure 3 This is a schematic diagram of the color-changing principle of the color-changing layer of the present invention (wherein 3A is the cellulose nanocrystal film in an unhumidified state; 3B is the cellulose nanocrystal film in a humidified state).

[0031] Figure 4 The following is a flowchart of the preparation process of the driver in this invention (the steps are: A-preparing a mixed solution; B-stirring; C-pouring the solution into a circular mold and drying at room temperature; D-irradiating with an ultraviolet lamp; E-cutting rectangular strips; F-pressing to form a film).

[0032] Figure 5 This is a schematic diagram of the fixture in this invention.

[0033] Figure 6 The following is a comparison chart of the electrical response test of an embodiment of the present invention (6A is in the unpowered state, and 6B is in the 2V DC voltage powered state).

[0034] Figure 7 The humidity test comparison diagrams of the present invention are shown in the figure (7A initial unhumidified state, 7B humidity stimulation state after adding water). Detailed Implementation

[0035] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0036] The preparation method provided by this invention is based on bio-friendly cellulose nanocrystals and carboxylated bacterial cellulose ionic electroactive actuators (existing technology). Through a simple pressure method, a deformable and color-changing flexible actuator based on cellulose can be finally obtained.

[0037] The cellulose-based deformable and color-changing flexible actuator has a three-layer structure: two color-changing cellulose nanocrystalline films on both sides and a carboxylated bacterial cellulose ionoactive actuator in the middle. When a voltage is applied across the electrodes, positive ions in the ionic liquid of the middle actuator move towards the negative electrode, while negative ions move towards the positive electrode. The difference in volume between the positive and negative ions causes contraction or expansion near the corresponding electrode materials, resulting in the bending and deflection of the actuator, thus enabling its driving function under voltage. When a humidity change stimulus is applied to the surface of the actuator, the pitch of the cholesteric levorotatory structure formed by the self-assembly of the color-changing layer increases, causing a change in the reflected wavelength. Consequently, the color reflected by the film redshifts, resulting in a color change.

[0038] Example 1

[0039] A method for preparing a cellulose-based deformable and color-changing flexible actuator includes the following steps:

[0040] Step 1): Prepare a humidity-responsive color-changing cellulose nanocrystal-polyethylene glycol diacrylate film;

[0041] Step 1.1): Mix 20 parts by weight of cellulose nanocrystal solution (PEDOT) and 0 parts by weight of polyethylene glycol diacrylate solution (PSS) to form a mixed solution;

[0042] Step 1.2): Seal and stir the aforementioned mixed solution for 3 hours;

[0043] Step 1.3): Pour the stirred mixture into a circular silicone mold with a diameter of 8cm and a depth of 1cm and dry at room temperature for 48 hours;

[0044] Step 1.4): Irradiate the dried cellulose film with a 250W ultraviolet lamp for 5 minutes;

[0045] Step 1.5): After cooling at room temperature for a period of time, remove the film and cut it into rectangular strips with sides of 15×45mm.

[0046] Step 2): Prepare sheet-like ion-type electroactive actuators based on carboxylated bacterial cellulose (existing technology, a high-performance flexible actuator, see CN112480457A);

[0047] Step 3): Fabricate a cellulose-based deformable and color-changing flexible actuator;

[0048] Step 3.1): Attach the rectangular strips to both sides of the ionotropic electroactive actuator based on carboxylated bacterial cellulose, and wrap it with filter paper;

[0049] Step 3.2) Place the wrapped membrane in the middle of the glass slide and use the clamp ( Figure 5 (As shown) Apply pressure at room temperature for 48-72 hours;

[0050] Step 3.3) Remove the membrane after pressing and cut it into rectangular strips of 10×40mm;

[0051] The prepared driver is placed in the storage instrument for later experimental testing.

[0052] Example 2

[0053] A method for preparing a cellulose-based deformable and color-changing flexible actuator includes the following steps:

[0054] Step 1): Prepare a humidity-responsive color-changing cellulose nanocrystal-polyethylene glycol diacrylate film;

[0055] Step 1.1): Mix 20 parts by weight of cellulose nanocrystal solution and 0.1 parts by weight of polyethylene glycol diacrylate solution to form a mixed solution;

[0056] Step 1.2): Seal and stir the aforementioned mixed solution for 3.5 hours;

[0057] Step 1.3): Pour the stirred mixture into a circular silicone mold with a diameter of 8cm and a depth of 1cm and dry at room temperature for 72 hours;

[0058] Step 1.4): Irradiate the dried cellulose film with a 250W ultraviolet lamp for 5 minutes;

[0059] Step 1.5): After cooling at room temperature for a period of time, remove the film and cut it into rectangular strips with sides of 15×45mm.

[0060] Step 2): Prepare sheet-like ion-type electroactive actuators based on carboxylated bacterial cellulose (existing technology, a high-performance flexible actuator, see CN112480457A);

[0061] Step 3): Fabricate a cellulose-based deformable and color-changing flexible actuator;

[0062] Step 3.1): Attach the rectangular strips to both sides of the ionotropic electroactive actuator based on carboxylated bacterial cellulose, and wrap it with filter paper;

[0063] Step 3.2) Place the wrapped membrane in the middle of the glass slide and use the clamp ( Figure 5 (As shown) Apply pressure at room temperature for 48-72 hours;

[0064] Step 3.3) Remove the membrane after pressing and cut it into rectangular strips of 10×40mm;

[0065] The prepared driver is placed in the storage instrument for later experimental testing.

[0066] Example 3

[0067] A method for preparing a cellulose-based deformable and color-changing flexible actuator includes the following steps:

[0068] Step 1): Prepare a humidity-responsive color-changing cellulose nanocrystal-polyethylene glycol diacrylate film;

[0069] Step 1.1): Mix 20 parts by weight of cellulose nanocrystal solution and 0.4 parts by weight of polyethylene glycol diacrylate solution to form a mixed solution;

[0070] Step 1.2): Seal and stir the aforementioned mixed solution for 4 hours;

[0071] Step 1.3): Pour the stirred mixture into a circular silicone mold with a diameter of 8cm and a depth of 1cm and dry at room temperature for 60 hours.

[0072] Step 1.4): Irradiate the dried cellulose film with a 250W ultraviolet lamp for 5 minutes;

[0073] Step 1.5): After cooling at room temperature for a period of time, remove the film and cut it into rectangular strips with sides of 15×45mm.

[0074] Step 2): Prepare sheet-like ion-type electroactive actuators based on carboxylated bacterial cellulose (existing technology, a high-performance flexible actuator, see CN112480457A);

[0075] Step 3): Fabricate a cellulose-based deformable and color-changing flexible actuator;

[0076] Step 3.1): Attach the rectangular strips to both sides of the ionotropic electroactive actuator based on carboxylated bacterial cellulose, and wrap it with filter paper;

[0077] Step 3.2) Place the wrapped membrane in the middle of the glass slide and use the clamp ( Figure 5 (As shown) Apply pressure at room temperature for 48-72 hours;

[0078] Step 3.3) Remove the membrane after pressing and cut it into rectangular strips of 10×40mm;

[0079] The prepared driver is placed in the storage instrument for later experimental testing.

[0080] The actuator prepared in the above embodiments still needs to be tested using an output displacement platform (existing device) and a humidifier. The prepared actuator is then placed in a storage instrument for later experimental testing.

[0081] The deformable and color-changing flexible actuator obtained by this invention can respond quickly and generate large bending deformation at low voltage, and can change color in response to changes in external humidity to adapt to different application scenarios.

[0082] Performance testing

[0083] 1. Electrical response test

[0084] The excitation response of the cellulose-based deformable and color-changing flexible actuator obtained from the test examples under 2V AD (i.e., DC) is shown in the test results. Figure 6 (6A is not powered on, 6B is powered on with 2V DC voltage), as shown in Appendix 1.

[0085] 2. Humidity response test

[0086] The color change of the cellulose-based deformable and color-changing flexible actuator obtained in the test example after humidity change is as follows: Figure 7 As shown in Figure 7A (7A is the initial unhumidified state diagram, and Figure 7B is the humidity stimulation state diagram after adding water).

[0087] 3. Performance Testing (See table below)

[0088] Table 1

[0089] Deformation Drive voltage Basic colors Humidity-responsive color Existing drives 3.5mm 4v none none Example 1 4.2mm 2v light blue light red Example 2 4.1mm 2v blue-green Orange-red Example 3 4.2mm 2v pale reddish-green Orange-red

[0090] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to describe its nature. Although the present invention has been described in detail with reference to the examples, those who have the same knowledge in the technical field of the present invention can modify and change the technical ideas of the present invention in various forms, and all of them should be covered within the scope of the claims of the present invention.

Claims

1. A method for fabricating a cellulose-based deformable and color-changing flexible actuator, comprising the following steps: Step 1) Preparation of a humidity-responsive color-changing cellulose nanocrystal-polyethylene glycol diacrylate film Step 1.1) Mix the cellulose nanocrystal solution and the polyethylene glycol diacrylate solution to form a mixed solution; Step 1.2) Mix the solutions prepared in Step 1.1 and stir under sealed conditions at room temperature to obtain a stable and uniform cellulose nanocrystal-polyethylene glycol diacrylate solution; Step 1.3) Pour the solution into the mold and allow it to dry at room temperature; Step 1.4) After drying, the obtained cellulose film is placed under a UV lamp for irradiation to obtain a cellulose nanocrystal-polyethylene glycol diacrylate composite film with variable color in response to humidity. Step 2) Preparation of ion-type electroactive actuators based on carboxylated bacterial cellulose; Step 3) Fabricate a deformable and color-changing flexible actuator using a pressure method: On both sides of the ion-type electroactive actuator based on carboxylated bacterial cellulose prepared in step 2, a cellulose nanocrystal-polyethylene glycol diacrylate composite film prepared in step 1 is respectively bonded, and then pressure composite is performed to finally obtain a flexible actuator based on cellulose that can deform and change color. The volume concentration of the cellulose nanocrystal solution in step 1.1) is 1%, and the volume concentration of the polyethylene glycol diacrylate solution is 5%. In step 1.1), the weight ratio of cellulose nanocrystal solution and polyethylene glycol diacrylate solution is 20-25:0-0.

2.

2. The method for preparing the cellulose-based deformable and color-changing flexible actuator according to claim 1, characterized in that: In step 1.2), the time for sealing and stirring at room temperature is 3 to 4 hours.

3. The method for preparing the cellulose-based deformable and color-changing flexible actuator according to claim 2, characterized in that: The drying in step 1.3) is carried out in a windless and static environment at room temperature for 48-72 hours.

4. The method for preparing the cellulose-based deformable and color-changing flexible actuator according to claim 3, characterized in that: The ultraviolet lamp power in step 1.3) is 100-400W, and the treatment time is 2-10 minutes.

5. In the method for preparing the cellulose-based deformable and color-changing flexible actuator according to claim 4, the bonding in step 3) involves cutting the obtained ion-type electroactive actuator based on carboxylated bacterial cellulose and the cellulose nanocrystal-polyethylene glycol diacrylate composite film into rectangular strips of suitable shape, and then aligning and stacking them.

6. The method for preparing the cellulose-based deformable and color-changing flexible actuator according to claim 5, characterized in that: The pressure composite preparation described in step 3) involves wrapping the aligned and stacked composite material with filter paper, placing it in the middle of a glass slide, and clamping it with a fixture for 48-72 hours.

Images