Humidity-responsive actuator and method of making and using same

Abstract

The present application relates to a kind of humidity response actuator and its preparation method and application, belong to actuator technical field.The humidity response actuator of the present application is double-layer film structure, including humidity response active layer and humidity response inert layer;The humidity response active layer is made into nanofiber membrane by electrospinning technology to hydrophilic polymer material, the nanofiber membrane has orientation structure;The humidity response inert layer is non-hydrophilic polymer film adhesive tape.The humidity response actuator of the present application due to the orientation structure of fiber, the deformation of humidity response actuator only occurs in fiber orientation direction, so it can be designed fiber orientation direction and the relative change of shape direction of humidity response actuator, realize the design and programming of humidity response actuator deformation mode.

Description

Technical Field

[0001] This invention belongs to the field of actuator technology, and particularly relates to a humidity-responsive actuator, its preparation method and application. Background Technology

[0002] Stimulus-responsive actuators are devices that undergo reversible morphological changes in response to external environmental stimuli, and they hold broad application prospects in fields such as environmental monitoring, medical diagnostics, artificial muscles, and soft robotics. Their stimuli include light, electricity, magnetism, temperature, humidity, and various gas molecules. Humidity-responsive actuators, in particular, are driven by changes in air humidity, i.e., the movement of water molecules. Their stimuli are widely available, and they possess immense application potential, thus attracting significant attention.

[0003] The inspiration for humidity response comes from plant movement. Plants lack a musculoskeletal structure, so most cannot move. However, some plants possess a unique double-layered structure, and combined with the moisture expansion properties of plant cells, they can perform simple, purposeful movements. Examples include the Venus flytrap capturing insects, the mimosa closing its leaves, and the pine cone releasing seeds. Taking the pine cone as an example, on sunny, dry days, the pine cone scales open; as rain approaches and humidity rises, the scales close; when mature, the scales automatically dehydrate and open to disperse the seeds. The pine cone seed is tightly encased in scales, which consist of a fibrous layer and a tunic. The tunic layer has a much higher coefficient of hygroscopic expansion than the fibrous layer. Therefore, upon absorbing moisture, the two layers experience a strain mismatch, deforming to achieve a specific movement.

[0004] Conventional thin-film humidity actuators use a cast thin film as the active layer, making it difficult for water molecules to penetrate the material and resulting in a slow response rate to humidity. Furthermore, their isotropic nature makes it impossible to control the deformation direction during humidity actuation. Controlling the deformation mode of a cast thin-film actuator requires creating an inert layer on the active layer using a mask, which significantly increases the operational complexity. Therefore, it is crucial to develop a simple actuator with a fast response and pre-programmable deformation mode. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a humidity-responsive actuator, its fabrication method, and its application. This humidity-responsive actuator possesses advantages such as high sensitivity, rapid response, large actuation deformation, and controllable deformation. By adjusting the orientation structure of the fibers in the humidity-responsive active layer, its humidity-responsive performance is improved, and the deformation mode can be preset and programmed.

[0006] The first objective of this invention is to provide a humidity-responsive actuator, which has a double-layer thin-film structure, including a humidity-responsive active layer and a humidity-responsive inert layer; the humidity-responsive active layer is a nanofiber membrane made of hydrophilic polymer material by electrospinning technology, and the nanofiber membrane has an oriented structure; the humidity-responsive inert layer is a non-hydrophilic polymer film tape.

[0007] In one embodiment of the present invention, the orientation structure refers to the axial distribution of fibers in the nanofiber membrane tending to be in the same direction; when the standard deviation of the fiber orientation angle in the nanofiber membrane is small, the degree of orientation is high, and when the standard deviation of the fiber orientation angle in the nanofiber membrane is large, the degree of orientation is low.

[0008] In one embodiment of the present invention, the angle between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 0°-90°.

[0009] Furthermore, when the included angle is 0°, the humidity-responsive actuator curls along the length direction; when the included angle is 90°, the humidity-responsive actuator curls along the width direction; when the included angle is any other arbitrary angle, it moves in a spiral curling form, and the angle can be adjusted to control the pitch of the spiral twist, thereby realizing the controllable deformation and programming of the humidity-responsive actuator.

[0010] In one embodiment of the present invention, the standard deviation of the fiber orientation angle in the nanofiber membrane is 5°-25°.

[0011] In one embodiment of the present invention, a controllable deformation humidity-responsive actuator can be obtained by cutting the nanofibers according to the orientation of the humidity-responsive active layer.

[0012] In one embodiment of the present invention, the hydrophilic polymer material is selected from one or more of polyethylene oxide (PEO), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyvinylpyrrolidone (PVP); in one embodiment of the present invention, the non-hydrophilic polymer film tape is selected from polyimide (PI) tape, polyethylene terephthalate (PET) tape, or polypropylene (PP) tape.

[0013] In one embodiment of the present invention, the thickness of the humidity-responsive active layer is 24μm-82μm, which is controlled by the electrospinning time; the thickness of the humidity-responsive inert layer is 30μm-40μm.

[0014] A second objective of this invention is to provide a method for preparing the humidity-responsive actuator, comprising the following steps:

[0015] S1. Dissolve the hydrophilic polymer material in a solvent to obtain a spinning solution;

[0016] S2. Electrospinning is performed on the spinning solution described in S1, and the prepared nanofiber membrane is dried to obtain a humidity-responsive active layer.

[0017] S3. A humidity-responsive inert layer is bonded to the humidity-responsive active layer described in S2 to obtain the humidity-responsive actuator.

[0018] In one embodiment of the present invention, in S1, the concentration of the spinning solution is 4wt%-8wt%.

[0019] In one embodiment of the present invention, in S1, the solvent is selected from one or more of water, ethanol, methanol, acetone, dichloromethane, trichloromethane, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide.

[0020] In one embodiment of the present invention, in S2, the process parameters of the electrospinning are as follows: spinning voltage is 16kV-20kV, receiving distance is 22cm-28cm, micro-pump speed is 0.7mL / h-1.0mL / h, and receiving device rotation speed is 800r / min-1500r / min.

[0021] In one embodiment of the present invention, in S2, the drying temperature is 35°C-50°C and the time is 5h-12h.

[0022] In one embodiment of the present invention, in S2, the preparation of the humidity-responsive actuator specifically includes the following steps: bonding the side of the humidity-responsive inert layer with adhesive to the humidity-responsive active layer and rolling to obtain the humidity-responsive actuator.

[0023] A third objective of this invention is to provide an application of the humidity-responsive actuator described above in intelligent response.

[0024] The technical solution of the present invention has the following advantages compared with the prior art:

[0025] (1) The preparation method described in this invention uses electrospinning technology to prepare a humidity-responsive active layer with an oriented structure, which greatly increases the specific surface area and pore structure of the humidity-responsive active layer moisture exchange material, making the water molecule entry and exit efficiency higher and more sensitive to humidity changes compared with traditional cast film actuators.

[0026] (2) The preparation method of this invention prepares a nanofiber membrane with an oriented structure by increasing the rotation speed of the spinning and collecting device, and uses it as a humidity-responsive active layer. When the fiber material absorbs water molecules and expands or releases water molecules and contracts, the stress generated by the expansion or contraction can be continuously transmitted in the fiber axial direction due to the continuity of the fiber material. In the fiber radial direction, the fiber itself can expand, but the fibers are not in complete contact with each other, with only a few contact points, making it difficult for the expansion to be continuously transmitted and accumulated. Therefore, unlike the isotropic nature of ordinary nanofiber membranes, the nanofiber membrane with an oriented structure can only transmit deformation along the orientation direction, and the strain mismatch of the humidity-responsive actuator only occurs in the fiber orientation direction. This makes the response stress of the humidity-responsive active layer more concentrated, the response deformation degree of the humidity-responsive actuator greater, and the actuation performance better.

[0027] (3) Due to the fiber orientation structure, the deformation of the humidity-responsive actuator described in this invention only occurs in the fiber orientation direction. Therefore, the design and programming of the deformation mode of the humidity-responsive actuator can be realized by designing the relative change between the fiber orientation direction and the shape direction of the humidity-responsive actuator. Attached Figure Description

[0028] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0029] Figure 1 This is a schematic diagram illustrating the manufacturing process, structure, and working principle of the humidity-responsive actuator of the present invention.

[0030] Figure 2 The images show the fiber microstructure of the nanofiber membranes prepared in Examples 1-2 and Comparative Examples 1-2 of this invention; where a is Comparative Example 1, b is Comparative Example 2, c is Example 1, and d is Example 2.

[0031] Figure 3 The standard deviation of the fiber orientation angle of the nanofiber membranes prepared in Examples 1-2 and Comparative Examples 1-2 of this invention; wherein, a1 is Comparative Example 1, b1 is Comparative Example 2, c1 is Example 1, and d1 is Example 2;

[0032] Figure 4 The bending actuation response performance of the humidity-responsive actuators prepared in Examples 1-2 and Comparative Examples 1-2 of the present invention when the ambient humidity changes from 40% to 90%;

[0033] Figure 5 The diagram shows a comparison of the actuation response speed of the actuators prepared in Example 2 and Comparative Example 3 under the same humidity change; where Comparative Example 3 is on the left and Example 2 is on the right.

[0034] Figure 6 The bending actuation response performance of the humidity-responsive actuators prepared in Examples 2-4 and Comparative Examples 4-5 of the present invention when the ambient humidity changes from 40% to 90%;

[0035] Figure 7 The deformation mode of the humidity-responsive actuator prepared in Examples 5-9 of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0037] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0038] In this invention, unless otherwise stated, the raw material information involved in the embodiments of this invention is as follows: PEO was purchased from Xiamen Nalai Technology Co., Ltd., with a molecular weight of 500,000; PVP was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a molecular weight of 1,300,000; PEG was purchased from Sinopharm Chemical Reagent Co., Ltd., with a molecular weight of 20,000; PVA was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with a model number of 1788; PI film tape was purchased from Shenzhen Hongzhan Adhesive Technology Co., Ltd.; PET film tape was purchased from Mingchao Adhesive Tape; PP film tape was purchased from Tesa Tape, with a model number of tesa4298.

[0039] In this invention, unless otherwise stated, the calculation method for the standard deviation of angles in the embodiments of this invention is as follows: The axial angles of the electrospun nanofibers in the electron microscope images are measured using ImageJ image processing software. Thirty fibers are randomly selected from each group. First, using the horizontal direction of the image as a baseline, the axial angles of these fibers are measured and the average value is taken as the overall orientation angle of the fiber membrane in this group. Then, using the normal direction of the orientation angle as a baseline, i.e., setting the orientation angle to 90°, the axial angles of the 30 fibers are recalculated and denoted as A1-A. 30 The standard deviation S of the angle is calculated using the following formula, which is used to characterize the distribution of the fiber axial angle:

[0040]

[0041] Example 1

[0042] Reference Figure 1 As shown, the humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0043] S1. Preparation of spinning solution: PEO is dissolved in deionized water and stirred thoroughly to obtain a spinning solution with a mass concentration of 6%.

[0044] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 18kV, receiving distance 28cm, micro-pump speed 0.9mL / h, and receiving device rotation speed 800r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 24μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 24.59°. The collected nanofiber membrane was placed in an oven and dried at 40℃ for 8h to obtain the humidity-responsive active layer.

[0045] S3. Preparation of humidity-responsive actuator: Select a PI film tape with a thickness of 35μm, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 5*20mm rectangular humidity-responsive actuator along the fiber orientation direction, that is, the angle formed between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 0°, thus obtaining a humidity-responsive actuator that is rolled up along the length direction.

[0046] Example 2

[0047] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0048] S1. Preparation of spinning solution: PEO is dissolved in deionized water and stirred thoroughly to obtain a spinning solution with a mass concentration of 6%.

[0049] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 18kV, receiving distance 28cm, micro-pump speed 0.9mL / h, and receiving device rotation speed 1200r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 24μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 9.06°. The collected nanofiber membrane was placed in an oven and dried at 40℃ for 8h to obtain the humidity-responsive active layer.

[0050] S3. Preparation of humidity-responsive actuator: Select a PI film tape with a thickness of 35μm, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 5*20mm rectangular humidity-responsive actuator along the fiber orientation direction, that is, the angle formed between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 0°, thus obtaining a humidity-responsive actuator that is rolled up along the length direction.

[0051] Example 3

[0052] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0053] The process is basically the same as in Example 2, except that the spinning time is changed to obtain a nanofiber membrane with a thickness of 35 μm, and a 5*20 mm rectangular humidity-responsive actuator is prepared in the same way.

[0054] Example 4

[0055] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0056] The process is basically the same as in Example 2, except that the spinning time is changed to obtain a nanofiber membrane with a thickness of 82 μm, and a 5*20 mm rectangular humidity-responsive actuator is prepared in the same way.

[0057] Example 5

[0058] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0059] S1. Preparation of spinning solution: PEO is dissolved in deionized water and stirred thoroughly to obtain a spinning solution with a mass concentration of 6%.

[0060] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 20kV, receiving distance 25cm, micro-pump speed 0.7mL / h, and receiving device rotation speed 1200r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 30μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 8.14°. The collected nanofiber membrane was placed in an oven and dried at 35℃ for 12h to obtain the humidity-responsive active layer.

[0061] S3. Preparation of humidity-responsive actuator: Select a PI film tape with a thickness of 35μm, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 5*30mm rectangular humidity-responsive actuator along the fiber orientation direction, that is, the angle formed between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 0°, thus obtaining a humidity-responsive actuator that is rolled up along the length direction.

[0062] Example 6

[0063] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0064] The process is basically the same as in Example 5, except that the angle between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is changed to 30° when the humidity-responsive actuator is cut, resulting in a spiral-curved humidity-responsive actuator.

[0065] Example 7

[0066] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0067] The process is basically the same as in Example 5, except that the angle between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is changed to 45° when the humidity-responsive actuator is cut, resulting in a spirally coiled humidity-responsive actuator.

[0068] Example 8

[0069] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0070] The process is basically the same as in Example 5, except that the angle between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is changed to 60° when the humidity-responsive actuator is cut, resulting in a spiral-curved humidity-responsive actuator.

[0071] Example 9

[0072] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0073] The process is basically the same as in Example 5, except that the angle between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is changed to 90° when the humidity-responsive actuator is cut, resulting in a humidity-responsive actuator that is curled along the width direction.

[0074] Example 10

[0075] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0076] S1. Preparation of spinning solution: PVP is dissolved in deionized water and stirred thoroughly to obtain a spinning solution with a mass concentration of 8%.

[0077] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 20kV, receiving distance 22cm, micro-pump speed 0.7mL / h, and receiving device rotation speed 1500r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 40μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 6.42°. The collected nanofiber membrane was placed in an oven and dried at 50℃ for 5h to obtain the humidity-responsive active layer.

[0078] S3. Preparation of humidity-responsive actuator: Select a 30μm thick PET film tape, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 5*30mm rectangular humidity-responsive actuator along the fiber orientation direction, that is, the angle between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 0°, thus obtaining a humidity-responsive actuator that is rolled up along the length direction.

[0079] Example 11

[0080] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0081] S1. Preparation of spinning solution: Dissolve PEG in deionized water and stir thoroughly to obtain a spinning solution with a mass concentration of 4%.

[0082] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 16kV, receiving distance 25cm, micro-pump speed 1.0mL / h, and receiving device rotation speed 1500r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 40μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 7.15°. The collected nanofiber membrane was placed in an oven and dried at 50℃ for 8h to obtain the humidity-responsive active layer.

[0083] S3. Preparation of humidity-responsive actuator: Select a PP film tape with a thickness of 40μm, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 5*30mm rectangular humidity-responsive actuator along the fiber orientation direction, that is, the angle formed between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 0°, thus obtaining a humidity-responsive actuator that is rolled up along the length direction.

[0084] Example 12

[0085] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0086] S1. Preparation of spinning solution: PVA is dissolved in deionized water and stirred thoroughly to obtain a spinning solution with a mass concentration of 7%.

[0087] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 18kV, receiving distance 25cm, micro-pump speed 0.8mL / h, and receiving device rotation speed 1200r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 30μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 8.73°. The collected nanofiber membrane was placed in an oven and dried at 45℃ for 10h to obtain the humidity-responsive active layer.

[0088] S3. Preparation of humidity-responsive actuator: Select a PI film tape with a thickness of 35μm, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 5*30mm rectangular humidity-responsive actuator at a 45° angle along the fiber orientation direction, that is, the angle formed between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 45°, thus obtaining a spirally curled humidity-responsive actuator.

[0089] Example 13

[0090] The humidity-responsive actuator and its preparation method of the present invention specifically include the following steps:

[0091] S1. Preparation of spinning solution: PVA and PVP are dissolved in deionized water at a mass ratio of 1:1 and stirred thoroughly to obtain a spinning solution with a mass concentration of 6%.

[0092] S2. Preparation of the humidity-responsive active layer: The spinning solution was loaded into an electrospinning device, and the electrospinning process parameters were set as follows: spinning voltage 18kV, receiving distance 25cm, micro-pump speed 0.9mL / h, and receiving device rotation speed 1200r / min. Electrospinning was performed to deposit nanofibers onto the release paper of the collecting roller. The spinning time was controlled to obtain a nanofiber membrane with a thickness of 24μm. The standard deviation of the fiber orientation angle in the nanofiber membrane was 9.48°. The collected nanofiber membrane was placed in an oven and dried at 45℃ for 10h to obtain the humidity-responsive active layer.

[0093] S3. Preparation of humidity-responsive actuator: Select a PI film tape with a thickness of 35μm, attach the adhesive side of the film tape to the nanofiber membrane, peel it off from the release paper, and roll it to obtain a double-layer composite film; cut it into a 10*30mm rectangular humidity-responsive actuator at a 90° angle along the fiber orientation direction, that is, the angle formed between the fiber orientation of the nanofiber membrane and the length direction of the humidity-responsive actuator is 90°, thus obtaining a humidity-responsive actuator that is curled in the width direction.

[0094] Comparative Example 1

[0095] It is basically the same as Example 1, except that the receiving device rotates at 0 r / min.

[0096] Comparative Example 2

[0097] It is basically the same as Example 1, except that the receiving device rotates at 400 r / min.

[0098] Comparative Example 3

[0099] The process is basically the same as in Example 2, except that the prepared double-layer composite film is placed in an oven at 70°C for 30 minutes while in a clamped state to melt the PEO fiber layer. Then it is cooled at room temperature (25°C) to form a dense PEO film, and finally a cast film actuator is formed.

[0100] Comparative Example 4

[0101] The process is basically the same as in Example 2, except that the spinning time is changed to obtain a nanofiber membrane with a thickness of 7 μm, and a rectangular humidity-responsive actuator of 5*20 mm is prepared in the same way.

[0102] Comparative Example 5

[0103] The process is basically the same as in Example 2, except that the spinning time is changed to obtain a nanofiber membrane with a thickness of 16 μm, and a 5*20 mm rectangular humidity-responsive actuator is prepared in the same way.

[0104] Test Example 1

[0105] Scanning electron microscope (SEM) images and fiber orientation distribution diagrams of the nanofiber membranes prepared in Examples 1-2 and Comparative Examples 1-2 are shown below. Figure 2-3 As shown. From Figure 2-3It can be seen that the nanofiber membrane of Example 1 exhibits a certain orientation, with an angular standard deviation of 24.59. The nanofiber membrane of Example 2 exhibits a better orientation, with an angular standard deviation of only 9.06. In Comparative Example 1, the nanofiber membrane at no winding speed has a randomly distributed fiber orientation, with an angular standard deviation of 41.16. In Comparative Example 2, some fibers of the nanofiber membrane have a certain orientation, but most fibers have low orientation, with an angular standard deviation of 35.78. It is evident that the nanofiber membranes of Comparative Examples 1-2 have lower fiber orientation, while the nanofiber membranes of Examples 1-2 have better fiber orientation.

[0106] Test Example 2

[0107] The humidity-responsive actuators (of the same specifications) prepared in Examples 1-2 and Comparative Examples 1-2 exhibit the following bending actuation response performance when the ambient humidity changes from 40% to 90%: Figure 4 As shown. From Figure 4 It can be seen that the bending deformation angle of the humidity-responsive actuator exhibits significant differences. At no rotation speed or low rotation speed, the fiber orientation is low, resulting in unconcentrated stress in the nanofiber membrane of the humidity-responsive actuator, poor actuation performance, and a small bending deformation angle. However, at a rotation speed of 800 r / min, the prepared humidity-responsive actuator exhibits a larger bending deformation angle, which is due to stress concentration caused by orientation, effectively enhancing the actuation performance. Compared to the humidity-responsive actuator prepared at a winding speed of 0 r / min, the maximum deformation of the humidity-responsive actuator prepared from the electrospun nanofiber membrane at a winding speed of 1200 r / min increases from 133.08° to 472.19°, an increase of 254.82%. This demonstrates that the fiber orientation structure of the humidity-responsive actuator nanofiber membrane can significantly improve driving performance, exhibiting a larger winding angle deformation than the humidity-responsive actuator with a lower orientation degree. Furthermore, due to the stress concentration phenomenon of oriented fibers, the humidity-responsive actuator with a highly oriented nanofiber membrane has a faster deformation speed. Figure 4 It can also be seen that, compared with the humidity-responsive actuator prepared by the 0 r / min winding process, the deformation speed of the humidity-responsive actuator in Example 2 increased from 17.99° / s to 44.59° / s in the first 5 seconds, an increase of 147.88%. This indicates a faster humidity response sensitivity. Therefore, it is evident that the humidity-responsive actuator prepared in this example has superior actuation performance due to the higher fiber orientation of the nanofiber membrane.

[0108] Test Example 3

[0109] The actuators (of the same specifications) prepared in Example 2 and Comparative Example 3 were subjected to an airflow with a relative humidity of 95% under an ambient humidity of 40%. The response times were compared, and the results are as follows: Figure 5 As shown. From Figure 5 It can be seen that when the actuator comes into contact with moisture, the humidity-responsive active layer absorbs moisture and expands, causing the actuator to bend towards the PI membrane. At 2 seconds, the actuator prepared in Example 2 has changed from forward bending to reverse bending, while the actuator in Comparative Example 3 is still in the forward bending state. After 4 seconds, the moisture disappears, water molecules in the humidity-responsive active layer transfer to the environment, and the actuator bends towards the humidity-responsive active layer. From 4 seconds to 8 seconds, the actuator in Comparative Example 3 shows almost no deformation, while the highly oriented nanofiber membrane actuator prepared in Example 2 has changed from reverse bending back to its original forward bending state. Furthermore, at 10 seconds, the nanofiber membrane actuator has returned to its pre-actuation shape, while the actuator in Comparative Example 3 only recovered a very small angle. This indicates that the oriented nanofiber membrane has a faster water molecule exchange capacity and deformation response capability, exhibiting higher response sensitivity.

[0110] Test Example 4

[0111] The actuation performance of the humidity-responsive actuators (of the same specifications) prepared in Examples 2-4 and Comparative Examples 4-5 is as follows: Figure 6 As shown. From Figure 6 From the trend lines, humidity-responsive actuators with active layer thicknesses of 7μm and 16μm both exhibited rapid deformation in the first 5 seconds followed by significant reverse deformation. Humidity-responsive actuators with active layer thicknesses of 24μm, 35μm, and 82μm showed better forward deformation and larger deformation angles, indicating that a thinner active layer would affect the stability of the actuator; a suitable thickness is necessary for good responsive deformation. Regarding response speed, the 7μm actuator with the thinnest active layer was the most sensitive at 53.53° / s, while the 82μm actuator with the thickest active layer was the slowest at 21.28° / s. Furthermore, the 35μm actuator exhibited the greatest deformation at 538.13°, exceeding that of the thickest 82μm actuator. This indicates that an excessively thick humidity-responsive active layer can introduce bending resistance, which will not only affect the sensitivity of the humidity-responsive actuator but also its actuation capability.

[0112] Test Example 5

[0113] The deformation patterns of the humidity-responsive actuators (of the same specifications) prepared in Examples 5-9 are as follows: Figure 7 As shown. From Figure 7As can be seen, due to the high degree of nanofiber orientation in the nanofiber membrane, when the angle between the nanofiber orientation and the length direction of the humidity-responsive actuator is 0°, the deformation caused by the absorption and release of moisture by the fibers is mainly transmitted along the fiber length direction, i.e., the orientation direction. Therefore, it manifests as a coiling deformation along the length direction of the rectangular humidity-responsive actuator. When the angle between the nanofiber orientation and the length direction of the humidity-responsive actuator is between 0° and 90°, since the deformation stress is transmitted along the fiber orientation direction, deformation only occurs in the fiber orientation direction, causing the humidity-responsive actuator to undergo a spiral coiling actuation deformation. Furthermore, as the angle increases, the pitch of the coiling deformation of the humidity-responsive actuator increases. Until the angle between the nanofiber orientation and the length direction of the humidity-responsive actuator reaches 90°, the pitch increases to infinity, meaning that the fiber orientation in the humidity-responsive actuator is consistent with the width direction, and the actuation deformation coils along the width direction. Therefore, the technical solution of this invention can achieve controllable deformation and programming of the humidity-responsive actuator.

[0114] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A humidity-responsive actuator, characterized in that, The humidity-responsive actuator has a double-layer thin-film structure, comprising a humidity-responsive active layer and a humidity-responsive inert layer. The humidity-responsive active layer is a nanofiber membrane made from hydrophilic polymer materials using electrospinning technology, and the nanofiber membrane has an oriented structure. The humidity-responsive inert layer is a non-hydrophilic polymer film tape. The angle between the fiber orientation of the nanofiber membrane and the longitudinal direction of the humidity-responsive actuator is 0°-90°. The standard deviation of the fiber orientation angle in the nanofiber membrane is 5°-25°. The thickness of the humidity-responsive active layer... The thickness of the humidity-responsive inert layer is 30μm-40μm; the concentration of the spinning solution in the electrospinning process is 4wt%-8wt%; the process parameters of the electrospinning are: spinning voltage of 16kV-20kV, receiving distance of 22cm-28cm, micro-pump speed of 0.7mL / h-1.0mL / h, and receiving device rotation speed of 800r / min-1500r / min; the drying temperature of the nanofiber membrane after electrospinning is 35℃-50℃, and the drying time is 5h-12h.

2. The humidity-responsive actuator according to claim 1, characterized in that, The hydrophilic polymer material is selected from one or more of polyethylene oxide, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone; the non-hydrophilic polymer film tape is selected from polyimide tape, polyethylene terephthalate tape, or polypropylene tape.

3. A method for preparing a humidity-responsive actuator according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Dissolve the hydrophilic polymer material in a solvent to obtain a spinning solution; S2. Electrospinning is performed on the spinning solution described in S1, and the prepared nanofiber membrane is dried to obtain a humidity-responsive active layer. S3. A humidity-responsive inert layer is bonded to the humidity-responsive active layer described in S2 to obtain the humidity-responsive actuator.

4. The application of the humidity-responsive actuator according to any one of claims 1-2 in intelligent response.

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