A hot-pressed deformed fiber membrane, its preparation method and application

Abstract

The present invention belongs to the field of flexible actuators, and relates to a thermally deformed fiber membrane and its preparation method and application. The fiber membrane includes multiple layers of micro-melted porous insulating polymer fiber membranes and one or more layers of stimulus-responsive enhancement membranes. Among them, the multiple layers of micro-melted porous insulating polymer fiber membranes are obtained by thermally pressing a porous insulating polymer fiber membrane in a single-layer or multi-layer structure; the stimulus-responsive enhancement membranes are sandwiched between the micro-melted porous insulating polymer fiber membranes and are compounded by thermally pressing to obtain a thermally deformed fiber membrane with a sandwich structure. The present invention can achieve driving deformation under the action of an external environmental stimulus source, and at the same time realize the monitoring and collection of electromagnetic radiation in the environment.

Description

Technical Field

[0001] The present invention belongs to the field of flexible actuators, and particularly relates to a hot-pressed deformed fiber membrane, a preparation method thereof, and an application thereof. Background Art

[0002] A flexible actuator is a device that can undergo reversible deformation under environmental stimuli. Compared with a rigid actuator, it can continuously deform and achieve complex shapes, and can assist people in completing tedious or dangerous tasks in narrow spaces and complex working environments. A flexible actuator requires that the material or device design can quickly absorb or release stimulus factors (such as light radiation, heat energy, moisture, electrons, etc.), convert them into mechanical energy, and simultaneously undergo deformation. The diverse stimulation methods in the environment ensure that such flexible actuators have the advantages of a wide range of energy sources, fast deformation response / recovery, and large driving stroke. The corresponding actuators have broad application prospects in the fields of intelligent control, stimulus factor management, environmental monitoring, sensing and manipulation, etc.

[0003] The performance of a stimulus-responsive actuator largely depends on the microporous characteristics of the active layer. The pore structure is beneficial to improving the incident, migration, and management of environmental stimulus factors. Micro-nano fiber membranes have important advantages in terms of flexibility and porosity. However, their fluffy and soft nature and poor mechanical properties limit their deformation. Therefore, it is of great significance to construct a dense structure material with microporous characteristics, which is expected to simultaneously improve the environmental response ability and mechanical deformation ability of the material. However, the existing processing methods cannot meet the precise regulation of the response active layer material, and it is difficult to effectively integrate various types of environmental response active materials and achieve high responsiveness and high stability of the device, which limits the further development and potential application of the actuator.

[0004] In addition, most current robots can only complete movements or operations in simple scenarios and do not have sensing capabilities. Therefore, endowing them with sensing capabilities is of great significance. Electromagnetic radiation (EMR) widely exists in various electronic products such as household appliances, medical devices, and industrial machinery, constituting an omnipresent dangerous environment and bringing serious harm to the human body. Traditional electromagnetic radiation detection devices mainly include electromagnetic field testers or probes, electromagnetic radiation monitors, electromagnetic induction couplers, etc., which rely on specific scenarios for testing. Although some portable testers improve convenience, they are still difficult to meet the real-time testing requirements of EMR characteristics. A flexible actuator with sensing capabilities has the advantage of eliminating time and space limitations and is expected to achieve real-time monitoring of EMR in different scenarios. Materials with microporous characteristics can provide more interfaces for interaction with the electric field, providing good conditions for the sensing of EMR. Therefore, constructing a dense structure response material with microporous characteristics is crucial for coordinating actuation response and improving the sensitivity of EMR detection. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a hot-pressed deformed fiber membrane, its preparation method and application, so as to break through the dilemmas of low environmental energy conversion efficiency of active response materials, poor interface stability of different functional layers, poor comprehensive driving performance and lack of sensing ability in the existing methods.

[0006] The present invention provides a hot-pressed deformed fiber membrane, which comprises multiple layers of micro-melted porous insulating polymer fiber membranes and single or multiple layers of stimulus-responsive enhancement membranes. Among them, the multiple layers of micro-melted porous insulating polymer fiber membranes are obtained by hot pressing a porous insulating polymer fiber membrane in a single or multiple layer structure; the micro-melting means that after the fiber membrane is hot-pressed, partial melting phenomenon appears in the fiber structure on the surface, forming a structure between a porous membrane and a dense membrane; the stimulus-responsive enhancement membranes are sandwiched between the porous insulating polymer fiber membranes and are compounded by hot pressing to form a hot-pressed deformed fiber membrane with a sandwich structure.

[0007] Preferably, the porous insulating polymer fiber membrane is obtained by spinning an insulating polymer solution.

[0008] More preferably, the insulating polymer includes one or several of polystyrene, polycarbonate, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polymethyl methacrylate, polyimide, polyamide, polyester, polyimide amide, polyether, poly(methyl acrylate), polyurethane, polyvinyl chloride, polyacrylonitrile, nylon polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, polyacrylic acid, ethylene-vinyl alcohol copolymer, polylactic acid, polymethyl methacrylate, polyvinylidene fluoride, poly(ethylene oxide).

[0009] Preferably, the external environmental stimulus source includes light, heat, electricity, moisture or magnetic field. Light stimuli include one or several of near-infrared light, ultraviolet light, visible light, sunlight, LED light, incandescent lamp, laser or simulated sunlight; heat stimuli include one or several of human body temperature, biological skin temperature, environmental temperature, heating table, oven, hot air, microwave heating, ultrasonic heating, hot air gun, heat release from chemical reaction; electrical stimuli are direct current or alternating current; the moisture source is environmental moisture or artificially applied moisture; the magnetic field stimulus source is a magnet or an electromagnet.

[0010] More preferably, the light stimulus is near-infrared light; the heat stimulus is a heating table; the electrical stimulus is direct current; the moisture source is artificially applied moisture; the magnetic field stimulus source is a magnet.

[0011] Preferably, the stimulus-responsive enhancement membrane is formed by compounding a stimulus-responsive matrix and a stimulus-responsive filler.

[0012] More preferably, when the stimulus-responsive reinforcing film is a light-stimulus-responsive reinforcing film or a heat-stimulus-responsive reinforcing film, the stimulus-responsive matrix is one or more of polyester, polyurethane, polyacrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, styrene-isoprene, ethylene-vinyl acetate, and polylactic acid; the stimulus-responsive filler is one or more of silver nanowires, gold nanowires, copper nanowires, zinc oxide nanoparticles, iron oxide nanoparticles, iron oxide nanoparticles, silver nanoparticles, gold nanoparticles, copper nanoparticles, graphite, graphene, graphene oxide, carbon black, carbon nanotubes, carbon nitride, transition metal carbides, and black phosphorus.

[0013] Most preferably, when the stimulus-responsive reinforcing film is a light-stimulus-responsive reinforcing film or a heat-stimulus-responsive reinforcing film, the stimulus-responsive matrix is polyvinylidene fluoride, and the stimulus-responsive filler is black phosphorus.

[0014] Furthermore, the black phosphorus is a black phosphorus dispersion obtained by ultrasonic exfoliation of black phosphorus crystals in N,N-dimethylformamide, where the mass-volume ratio of black phosphorus to N,N-dimethylformamide is 1 g:10 mL to 1 g:100 mL.

[0015] More preferably, when the stimulus-responsive reinforcing film is an electric-stimulus-responsive reinforcing film, the stimulus-responsive matrix is one or more of metal nanofilms, conductive polymer films, and composites of polymers and conductive fillers; the stimulus-responsive filler is one or more of graphite, carbon black, graphene, carbon nanotubes, acetylene black, silver nanoparticles, gold nanoparticles, copper nanoparticles, nickel powder, silver nanowires, gold nanowires, copper nanowires, metal oxide powders, conductive polymers, and transition metal carbides / nitrides.

[0016] Most preferably, when the stimulus-responsive reinforcing film is an electric-stimulus-responsive reinforcing film, the stimulus-responsive matrix is a composite of a polymer and a conductive filler, and the stimulus-responsive filler is graphene.

[0017] More preferably, when the stimulus-responsive reinforcing film is a moisture-stimulus-responsive reinforcing film, the stimulus-responsive matrix is one or more of viscose, silk fibroin, cellulose, chitosan, sodium alginate, polyethylene oxide, polyvinyl alcohol, polyvinyl butyral, and polyvinylpyrrolidone; the stimulus-responsive filler is one or more of metal-organic frameworks, carbon-based materials, conductive polymers, transition metal carbides / nitrides, potassium titanate, polyacrylamide, and agar.

[0018] Most preferably, when the stimulus-responsive reinforcing film is a moisture-stimulus-responsive reinforcing film, the stimulus-responsive matrix is polyethylene oxide, and the stimulus-responsive filler is zirconium-based metal-organic framework UiO-66-NH 2 。

[0019] More preferably, when the stimulus-responsive enhanced film is a magnetic field stimulus-responsive enhanced film, the stimulus-responsive matrix is one or more of magnetic tape, magnetic film, and a composite of polymer and magnetic filler; the stimulus-responsive filler is one or more of magnetite nanoparticles, iron oxide nanoparticles, ferrite particles, neodymium iron boron particles, iron powder, nickel powder, cobalt powder, and cobalt iron particles.

[0020] Most preferably, when the stimulus-responsive enhanced film is a magnetic field stimulus-responsive enhanced film, the stimulus-responsive matrix is a composite of polymer and magnetic filler, and the stimulus-responsive filler is magnetite nanoparticles.

[0021] Preferably, the composite method is one or more of mixing, wrapping, core-shell, and embedding.

[0022] Most preferably, the composite method is mixing.

[0023] More preferably, the forming method is one or more of casting method, doctor blade coating method, flow coating method, brush coating method, and vacuum filtration method.

[0024] Most preferably, the forming method is the casting method, and the process parameters are: the adjustment range of the doctor blade is 100 - 1000 μm, the vacuum drying temperature of the film is 20 - 100 °C, and the drying time is 1 - 10 h.

[0025] Preferably, the thickness ratio of the micro-melted porous insulating polymer fiber membrane to the stimulus-responsive enhanced film is 10:1 to 1:10.

[0026] The present invention also provides a preparation method of a hot-pressed deformed fiber membrane, comprising the following steps:

[0027] (1) Mix an insulating polymer and a solvent, and stir to obtain a polymer solution; spin the polymer solution to obtain a porous insulating polymer fiber membrane;

[0028] (2) Hot-press the porous insulating polymer fiber membrane in a single-layer or multi-layer structure to obtain a multi-layer micro-melted porous insulating polymer fiber membrane;

[0029] (3) Mix a stimulus-responsive matrix, a stimulus-responsive filler, and a solvent to obtain a mixed solution; perform film-forming processing on the mixed solution to obtain a stimulus-responsive enhanced film;

[0030] (4) Sandwich the stimulus-responsive enhanced film between the multi-layer micro-melted porous insulating polymer fiber membranes and composite them by hot-pressing to obtain a hot-pressed deformed fiber membrane with a sandwich structure.

[0031] Preferably, the solvents in the steps (1) and (2) include one or more of deionized water, ethanol, methanol, isopropanol, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, chloroform, acetone, toluene, pyridine, thionyl chloride, and formic acid.

[0032] Preferably, the spinning in the step (1) includes one or more of electrospinning, melt spinning, microfluidic spinning, wet spinning, and dry spinning.

[0033] More preferably, the spinning is electrospinning.

[0034] Furthermore, the spinning environment temperature is 20 - 40 °C, the humidity is 20 - 90%, the polymer concentration in the polymer solution (i.e., spinning solution) is 1 wt% - 50 wt%, the stirring temperature of the spinning solution is 20 - 100 °C, the stirring time is 1 - 24 h, the spinning voltage is 1 - 35 kV, the receiving distance is 1 - 20 cm, and the roller speed is 100 - 2000 r.

[0035] Preferably, the mass ratio of the stimulus-responsive matrix to the stimulus-responsive filler in the step (3) is 1:10 - 200:1.

[0036] Preferably, the film-forming process in the step (3) is specifically: casting and vacuum drying; the parameters are that the blade adjustment range is 100 - 1000 μm, the drying temperature is 20 - 150 °C, and the drying time is 1 - 10 h.

[0037] Preferably, the hot pressing process parameters in the steps (2) and (4) are: the hot pressing pressure is 0.1 - 30 MPa, the hot pressing temperature is 50 - 250 °C, and the hot pressing time is 0.1 - 60 min.

[0038] During the multi-layer film composite process of the present invention, by changing the hot pressing conditions, including temperature, pressure, and time, hot pressing deformed fiber membranes with different characteristics can be obtained. In terms of temperature, it is selected according to the fiber material characteristics and thermal stability. At a lower temperature, a fiber membrane in an unmelted or partially melted state can be obtained, making the fiber membrane appear opaque or semi-transparent; at a higher temperature, a fiber membrane in a mostly melted and mutually adhered state can be obtained, making the fiber membrane appear highly transparent. For polyvinylidene fluoride, its melting temperature is usually between 150 and 175 °C. Therefore, when hot pressing a polyvinylidene fluoride fiber membrane, applying a temperature between 50 and 150 °C can achieve partial melting of the fiber membrane, while a temperature between 150 and 250 °C can achieve mostly melting or complete melting of the fiber membrane. In terms of pressure, appropriate pressure can change the morphology and mechanical properties of the fiber membrane. A lower pressure retains the original morphology and structure, while a higher pressure helps with melting and morphological changes. For polyvinylidene fluoride, when the applied temperature is between 50 and 100 °C and the pressure is between 0.1 and 20 MPa, the fiber structure can be better retained, while when the pressure is between 20 and 30 MPa, the fiber structure melts significantly. Adjusting the time parameter can affect the morphology and mechanical properties of the fiber membrane. A short time usually results in incomplete melting, and a long time usually results in excessive melting. For polyvinylidene fluoride, when the applied temperature is between 50 and 100 °C, the pressure is between 0.1 and 20 MPa, and the time is between 0.1 and 20 min, the melting degree of the fiber structure is relatively low, while when the time is between 20 and 60 min, the fiber melting degree is relatively large.

[0039] The present invention also provides an application of the hot pressing deformed fiber membrane in the fields of energy, information, medical treatment, or intelligent response.

[0040] Preferably, the application in the energy field includes energy harvesting or energy management devices.

[0041] Preferably, the application in the information field includes sensing or information interaction devices.

[0042] Preferably, the application in the medical field includes flexible or wearable medical devices.

[0043] Preferably, the application in the intelligent response field includes applications in artificial muscles, soft robots, or human-machine interaction.

[0044] Furthermore, the hot pressing deformed fiber membrane is compounded with an inert conductive adhesive tape, and a conductive layer is sputtered on the other side of the hot pressing deformed fiber membrane by a gold spraying process to obtain a composite actuator with a sandwich structure. It can achieve driving deformation under the action of an external environmental stimulus source, and at the same time, monitor and collect electromagnetic radiation in the environment.

[0045] Preferably, the gold spraying process parameters in step (5) are: the current is 10 - 50 mA, and the time is 60 - 300 s.

[0046] byFigure 1 It can be seen that after the fiber membrane is heat-pressed, partial melting occurs in the fiber structure on the surface, forming a microporous structure between the dense membrane and the porous membrane. There are both dense and porous regions in the thin film. This structure has a relatively uniform surface morphology and a high porosity, and also has a certain mechanical strength and stability.

[0047] It can be seen from Figure 3 that at wavelengths of 300 - 800 nm, the optical transmittance of the electrospun membrane is about 30%, with extremely low transparency; the optical transmittance of the cast membrane is about 98%, with extremely high transparency; the optical transmittance of the heat-pressed membrane is about 69%, between the electrospun membrane and the cast membrane, and the thin film is semi-transparent. Moderate optical transmittance is conducive to light incidence and accommodation, and can improve the photothermal conversion efficiency of the thin film.

[0048] It can be seen from Figure 4 that under the same infrared radiation power, the heat-pressed membrane shows a faster photothermal conversion efficiency, and can usually be heated to 57°C within 150 seconds, higher than the electrospun membrane (47.5°C) and the cast membrane (52°C). This indicates that the fiber membrane with a good balance of light transmittance and porosity effectively improves the photothermal conversion ability. The reasons can be attributed to: First, the high transparency of the heat-pressed membrane allows more light to enter the thin film. At the same time, the thin film structure with good porosity provides a bending path per unit area for the reflection, refraction, and scattering of light, enabling the light to be fully converted into heat.

[0049] It can be seen from Figure 5 that for the three kinds of thin films with the same thickness (about 40 μm), the tensile stress of the electrospun membrane is 4 MPa, and the elongation at break is 165%; the tensile stress of the cast membrane is 20 MPa, and the elongation at break is 12%; the tensile stress of the heat-pressed membrane is 13 MPa, and the elongation at break is 110%, between the electrospun membrane and the cast membrane. The heat-pressed membrane provides appropriate flexibility and stiffness, and has enhanced mechanical properties, which is conducive to achieving good driving deformation effects.

[0050] It can be seen from Figure 6 that for the three kinds of thin films with the same thickness (about 40 μm), the force generated when the cast membrane is bent is 80 cN. Due to the large flexibility of the electrospun membrane, the sensor cannot detect the force generated when it is compressed. In contrast, the force generated when the heat-pressed membrane is bent is 28 cN, between the electrospun membrane and the cast membrane, and can provide appropriate stiffness, which is conducive to achieving good driving deformation effects.

[0051] It can be seen from Figure 7It can be seen that a hot-pressed deformed fiber membrane is compounded with an inert conductive adhesive tape, and a conductive layer is sputtered on the other side of the fiber membrane through a gold spraying process to obtain an actuator with a composite sandwich structure (including upper and lower electrodes for sensing changes in the surrounding electromagnetic field, and a hot-pressed deformed film insulation interlayer for isolating the upper and lower electrodes). When the external magnetic field changes, a potential difference is generated between the electrodes to monitor the surrounding electromagnetic radiation.

[0052] It can be seen from Figure 8 that the porous structure has a high dielectric constant and a low dissipation factor because its pore structure can provide more interfaces to interact with the electric field and effectively block the energy dissipation in the electric field, providing good conditions for sensing electromagnetic radiation. Therefore, the hot-pressed deformed fiber membrane with porous characteristics can provide good sensing ability while maintaining excellent actuation performance.

[0053] It can be seen from Figure 9 that the composite sandwich structure actuator made of a hot-pressed deformed fiber membrane can dynamically sense the intensity of the surrounding electromagnetic radiation ( Figure 9 a) and distance ( Figure 9 b), and has high sensitivity ( Figure 9 c, d), can realize monitoring while walking ( Figure 9 e), and can also collect the electromagnetic radiation in the surrounding environment ( Figure 9 f).

[0054] Beneficial effects

[0055] (1) The present invention uses a spinning technology to prepare a porous fiber membrane. Specifically, spinnable polymers with different stimulus responses and stimulus-responsive fillers are selected for spinning to prepare a stimulus-responsive nanofiber thin film. Its porous structure and high specific surface area allow for the rapid absorption, effective propagation and diffusion, migration, and release of various light, heat, electricity, humidity, and magnetic stimulus factors. In addition, the porous structure can provide more interfaces to interact with the electric field, providing good conditions for the sensing of EMR. At the same time, the spun fiber membrane has micro-nano scale tunability and customizability, and it is easy to achieve precise modulation of fiber diameter, density, arrangement pattern, and layer thickness through process parameter adjustment.

[0056] (2) The hot-pressed deformed fiber membrane involved in the present invention constructs a micro-melted porous insulating polymer fiber membrane with a dense micro-porous characteristic structure through a hot-pressing process. Since the film has both high porosity and density, it can improve the incident property, migration property and control property of the environmental stimulus factors on the active layer of the actuator, and at the same time is beneficial to the protection of the inner active substances. In addition, the hot-pressing process can improve the problem that the mechanical properties of the traditional spun fiber membrane are often low due to the relatively loose fiber structure and the insufficiently tight connection between fibers. Through hot-pressing, the fibers are tightly connected and adhered to each other, further improving the mechanical properties and stability of the fiber membrane, and enhancing its driving response performance and deformation ability to various stimuli.

[0057] (3) The hot-pressed deformed fiber membrane involved in the present invention is composed of a micro-melted porous insulating polymer fiber layer and a stimulus-responsive enhancement layer. The micro-melted porous insulating polymer fiber membranes on both sides can improve the incident property of the stimulus-responsive factors and effectively protect the stimulus-responsive fillers, preventing them from contacting the air and oxidizing and failing. The inner stimulus-responsive enhancement sandwich layer can enhance the overall stimulus responsiveness and mechanical properties of the actuator, realizing the properties of high stiffness, high-efficiency energy conversion ability, large deformation, fast response and fast recovery of the material. In addition, the distribution, thickness and patterning of the stimulus-responsive enhancement film obtained by various forming processes in the micro-melted porous insulating polymer fiber membrane can be easily adjusted, so as to achieve local actuation and complex deformation effects. By configuring different stimulus-responsive enhancement layers, it is easy to achieve multiple responses. The preparation process flow of the hot-pressed deformed fiber membrane developed in the present invention is simple, the process conditions are mild, the controllability is high, the requirements for materials and processing environment are low, the adjustability of the components and structural properties is strong, and the potential for large-scale production is great.

[0058] (4) The hot-pressed deformed fiber membrane involved in the present invention is compounded with a conductive layer to obtain an actuator with a sandwich structure, which can achieve bending deformation under near-infrared light, heat, electricity, moisture and magnetic stimulation, and at the same time realize the monitoring and collection of electromagnetic radiation in the environment. The preparation strategy of the present invention is applicable to various functional materials, and the stimulus-responsive hot-pressed deformed fiber membrane can be customized according to different response requirements. Description of the Drawings

[0059] Figure 1 It is the SEM image of the hot-pressed deformed fiber membrane of the present invention.

[0060] Figure 2 It is the schematic diagram of the curvature calculation of the present invention.

[0061] Figure 3 It is the visible light transmittance of the film obtained by electrospinning, casting and hot-pressing of the present invention.

[0062] Figure 4 It is the photothermal conversion efficiency of the film obtained by electrospinning, casting and hot-pressing of the present invention.

[0063] Figure 5 These are the stress-strain curves of the thin films obtained by electrospinning, casting, and hot pressing in the present invention.

[0064] Figure 6 These are the force-displacement curves when the thin films obtained by electrospinning, casting, and hot pressing in the present invention are bent.

[0065] Figure 7 These are the schematic diagrams of electromagnetic radiation induction of the sandwich-structured actuator prepared by combining a thermally pressed deformed film and a conductive electrode in the present invention.

[0066] Figure 8 These are the dielectric constants and dissipation factors of the PVDF thin films obtained by electrospinning and casting in the present invention.

[0067] Figure 9 These are the perception of the sandwich-structured actuator prepared by combining a thermally pressed deformed film and a conductive electrode in the present invention for the electromagnetic radiation intensity (a) and distance (b) in the environment, the sensitivity (c, d) of monitoring the electromagnetic radiation intensity and distance, the display of monitoring while walking (e), and the capacitance charging curve (f).

[0068] Figure 10 These are the driving effects of the photo-thermal responsive thermally pressed deformed fiber film in Example 1.

[0069] Figure 11 These are the cyclic heating curves of the thermally pressed deformed fiber film before and after adding black phosphorus in Example 1.

[0070] Figure 12 These are the driving effects of the temperature responsive thermally pressed deformed fiber film in Example 2.

[0071] Figure 13 These are the driving effects of the humidity responsive thermally pressed deformed fiber film in Example 3.

[0072] Figure 14 These are the driving effects of the electro-responsive thermally pressed deformed fiber film in Example 4.

[0073] Figure 15 These are the driving effects of the magnetic responsive thermally pressed deformed fiber film in Example 5. Detailed implementation manners

[0074] The following further elaborates the present invention in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0075] The test method for the driving effect of the thermally pressed deformed fiber film in the embodiment is as follows:

[0076] (1) The optothermal stimulus source is provided by a near-infrared lamp. The test environment is a sealed transparent box. The thermal radiation of the thermoresponsive layer is realized by triggering the near-infrared lamp switch through a button; the thermal stimulus source is provided by a heating table. The heating table is set to 60 °C. Different temperature switching is realized by placing the driver on or removing it from the heating table; the electrical stimulus is provided by a DC power supply, and the device drive is realized by adjusting the DC voltage; the wet stimulus source is provided by a humidifier. The test environment is a sealed transparent box. The humidity control is realized by triggering the humidifier switch through a button. During this period, a humidity sensor recorder is used to provide accurate humidity data support; the magnetic stimulus is provided by a neodymium iron boron magnet. The drive is realized by adjusting the magnetic field by bringing the magnet closer to and away from the driver. The driving process is recorded by a high-definition camera.

[0077] (2) As Figure 2 shown, the angle in the case of being perpendicular to the horizontal plane is defined as 0°. The right side of this angle is defined as the negative angle, and vice versa, the left side is defined as the positive angle. Based on this, the driving behavior and performance of the asymmetric deformation-responsive fiber membrane are quantitatively processed. By measuring the bending angle before and after the stimulus, the corresponding curvature (K) can be calculated, and the change in curvature (K) is used to evaluate the driving effect. K can be expressed as:

[0078] K = 1 / R = (θ × π) / (180° × L),

[0079] In the formula, R: radius of curvature (unit: cm); θ: change angle (unit: °); L: arc length (unit: cm).

[0080] Example 1

[0081] In this example, an opto-thermal responsive thermally pressed deformed fiber membrane is provided. The preparation method is as follows: First, polyvinylidene fluoride is dissolved in N,N-dimethylformamide / acetone with a ratio of 7:3. The stirring temperature is 60 °C, and the stirring time is 7 h to prepare a spinning solution with a concentration of 10 wt%. Under the conditions of an environmental temperature of 25 °C and an environmental humidity of 50%, at a voltage of 15 kV, a receiving distance of 15 cm, a rotation speed of 500 r, and 1.5 mL h -1Electrospinning was carried out with electrospinning parameters to obtain a porous fiber membrane with a thickness of 80 μm. The porous fiber membrane was placed between hot pressing plates, and under the conditions of a hot pressing temperature of 80 °C, a hot pressing pressure of 15 MPa, and a hot pressing time of 1 min, a hot pressed fiber membrane with a thickness of 30 μm was obtained. Secondly, black phosphorus crystals and N,N-dimethylformamide with a mass ratio of 1:100 were weighed and ultrasonicated for 6 h to obtain a silver-gray black phosphorus dispersion. A casting solution with a concentration of 10 wt% was prepared by dissolving polyvinylidene fluoride in the black phosphorus dispersion, where the mass ratio of black phosphorus to polyvinylidene fluoride was 1:100. Then, the casting solution was poured onto a glass substrate, leveled with a 500-μm scraper, and placed in a vacuum oven to be heated at 60 °C for 6 h for vacuum drying. After cooling to room temperature, the polymer film was peeled off from the substrate to obtain a stimulus-responsive enhanced casting film with a thickness of 40 μm. Finally, the stimulus-responsive enhanced casting film was sandwiched between the hot pressed fiber membranes for hot pressing, where the hot pressing temperature was 100 °C, the hot pressing pressure was 20 MPa, and the hot pressing time was 3 min, to obtain a hot pressed deformed fiber membrane with a thickness of 70 μm. This fiber membrane can produce a responsive deformation to near-infrared light (such as Figure 10 ).

[0082] As Figure 11 can be seen, the hot pressed film containing black phosphorus has a higher heating rate than the hot pressed film without black phosphorus, which benefits from the fact that black phosphorus has a high near-infrared photothermal conversion ability, which can improve the heating rate of the film.

[0083] Example 2

[0084] In this example, a light-thermoresponsive hot pressed deformed fiber membrane was provided, and the preparation method was as follows: First, polyurethane was dissolved in N,N-dimethylformamide and stirred at room temperature for 6 h to prepare a spinning solution with a concentration of 12 wt%. Under the conditions of an ambient temperature of 30 °C and an ambient humidity of 60%, at a voltage of 30 kV, a receiving distance of 15 cm, and a rotation speed of 500 r, 1.5 mL h -1Electrospinning was carried out with electrospinning parameters to obtain a porous fiber membrane with a thickness of 50 μm. The porous fiber membrane was placed between hot pressing plates, and under the conditions of a hot pressing temperature of 40 °C, a hot pressing pressure of 10 MPa, and a hot pressing time of 2 min, a hot pressed fiber membrane with a thickness of 20 μm was obtained. Secondly, graphite and polyurethane with a mass ratio of 1:50 were weighed and dissolved in N,N-dimethylformamide to prepare a casting solution with a concentration of 10 wt%. Then, the casting solution was poured onto a glass substrate, leveled with a 200-μm doctor blade, and placed in a vacuum oven to be dried at 80 °C for 6 h. After cooling to room temperature, the polymer film was peeled off from the substrate to obtain a stimulus-responsive enhanced casting film with a thickness of 20 μm. Finally, the stimulus-responsive enhanced casting film was sandwiched between the hot pressed fiber membranes for hot pressing, where the hot pressing temperature was 60 °C, the hot pressing pressure was 15 MPa, and the hot pressing time was 3 min, to obtain a hot pressed deformed fiber membrane with a thickness of 55 μm. This fiber membrane can produce a responsive deformation to temperature (such as Figure 12 ).

[0085] Example 3

[0086] In this example, a humidity-responsive hot pressed deformed fiber membrane was provided, and the preparation method was as follows: First, polyethylene oxide was dissolved in deionized water to prepare a spinning solution with a concentration of 5 wt%, and a certain amount of metal-organic framework UiO-66-NH 2 was added as a humidity-responsive filler to the spinning solution, where the mass ratio of UiO-66-NH 2 to polyethylene oxide was 1:10. Electrospinning was carried out at a voltage of 20 kV, a receiving distance of 15 cm, a rotation speed of 1500 r, and a rate of 1.0 mL h -1 to obtain a porous fiber membrane with a thickness of 45 μm. The porous fiber membrane was placed between hot pressing plates, and under the conditions of a hot pressing temperature of 30 °C, a hot pressing pressure of 5 MPa, and a hot pressing time of 1 min, a hot pressed fiber membrane with a thickness of 30 μm was obtained. This hot pressed fiber membrane can produce a repeated responsive deformation to humidity (such as Figure 13 ).

[0087] Example 4

[0088] In this example, an electric-responsive hot pressed deformed fiber membrane was provided, and the preparation method was as follows: First, polyvinylidene fluoride was dissolved in N,N-dimethylformamide / acetone with a ratio of 7:3, the stirring temperature was 60 °C, and the stirring time was 8 h to prepare a spinning solution with a concentration of 12 wt%. Under the conditions of an ambient temperature of 25 °C and an ambient humidity of 50%, a certain amount of graphene was weighed and added as a conductive filler to the spinning solution, where the mass ratio of graphene to the polymer was 1:20. Electrospinning was carried out at a voltage of 16 kV, a receiving distance of 15 cm, a rotation speed of 1500 r, and a rate of 1.5 mL h -1Electrospinning was carried out with electrospinning parameters to obtain a porous fiber membrane with a thickness of 80 μm. The porous fiber membrane was placed between hot pressing plates, and under the conditions of a hot pressing temperature of 70 °C, a hot pressing pressure of 10 MPa, and a hot pressing time of 1.5 min, a hot pressed fiber membrane with a thickness of 50 μm was obtained. The hot pressed fiber membrane can produce a responsive deformation to electrical stimulation (such as Figure 14 ).

[0089] Example 5

[0090] In this example, a magnetoresponsive hot pressed deformation fiber membrane was provided, and the preparation method was as follows: First, polyvinylidene fluoride was dissolved in N,N-dimethylformamide / acetone with a ratio of 7:3, the stirring temperature was 60 °C, and the stirring time was 8 h to prepare a spinning solution with a concentration of 13 wt%. A certain amount of iron oxide nanoparticles was weighed as a magnetic filler and added to the spinning solution. The mass ratio of iron oxide nanoparticles to the polymer was 1:15. Under the conditions of an ambient temperature of 25 °C and an ambient humidity of 50%, at a voltage of 20 kV, a receiving distance of 15 cm, a rotation speed of 500 r, and 2.0 mL / h -1 Electrospinning was carried out with electrospinning parameters to obtain a porous fiber membrane with a thickness of 100 μm. The porous fiber membrane was placed between hot pressing plates, and under the conditions of a hot pressing temperature of 70 °C, a hot pressing pressure of 20 MPa, and a hot pressing time of 2 min, a hot pressed fiber membrane with a thickness of 65 μm was obtained. The hot pressed fiber membrane can produce a responsive deformation to a magnet (such as Figure 15 ).

[0091] Comparative Example 1

[0092] Thermoplastic polyurethane was dissolved in a mixed solvent with a volume ratio of THF:DMF of 7:3 at a concentration of 10 wt% for electrospinning. At room temperature, a thermoplastic polyurethane submicron fiber membrane was prepared by electrospinning at a spinning speed of 1.0 mL / h and a spinning voltage of 12 kV. By densely stacking multiple layers of such prepared submicron fiber membranes, a thermoplastic polyurethane nonwoven fabric with a thickness of 0.2 mm was obtained. Then, gelatin was dissolved in a mixed solvent with a volume ratio of acetic acid:ethyl acetate:deionized water of 6:3:1 at a concentration of 15 wt%, and the same amount of glycerol was added to the solution by stirring to obtain a solution of gelatin and glycerol. Then, the solution of gelatin and glycerol was sprayed into the thermoplastic polyurethane nonwoven fabric, and the sample was hot pressed and vacuum dried at 28 °C for 72 hours to completely remove the solvent. Finally, a gelatin-glycerol / thermoplastic polyurethane composite material with a thickness of 0.2 mm was prepared by vacuum hot pressing at 110 °C for 10 min. This material has a large actuation strain (5.2%) and high mechanical strength at an ultra-low voltage (0.5 kV mm -1 ).

Claims

1. A heat-pressed deformable fiber membrane, characterized in that: The heat-pressed deformable fiber membrane includes a micro-melting porous insulating polymer fiber membrane and a single-layer or multi-layer stimulus responsive enhancement membrane, wherein the micro-melting porous insulating polymer fiber membrane is obtained by hot pressing a porous insulating polymer fiber membrane in a single-layer or multi-layer structure; the micro-melting refers to that after the fiber membrane is subjected to hot pressing treatment, the fiber structure on the surface partially melts, forming a structure between a porous membrane and a dense membrane; the stimulus responsive enhancement membrane is sandwiched between the micro-melting porous insulating polymer fiber membranes, and is composited by hot pressing to form a heat-pressed deformable fiber membrane with a sandwich structure; the stimulus responsive enhancement membrane is compositely formed by a stimulus responsive matrix and a stimulus responsive filler.

2. The heat-compression-deformable fiber membrane according to claim 1, characterized in that: The micro-melting porous insulating polymer fiber membrane is obtained by spinning an insulating polymer solution.

3. The heat-compression-deformed fiber membrane according to claim 1, characterized in that: The external environmental stimulus source of the stimulus response enhancement film includes light, heat, electricity, moisture or magnetic field.

4. The heat-compression-deformable fiber membrane according to claim 1, characterized in that: When the stimulus response enhancement film is a light stimulus response enhancement film or a thermal stimulus response enhancement film, the stimulus response matrix is ​​one or more of polyester, polyurethane, polyacrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, styrene-isoprene, ethylene-vinyl acetate, and polylactic acid; the stimulus response filler is one or more of silver nanowires, gold nanowires, copper nanowires, zinc oxide nanoparticles, ferrous oxide nanoparticles, iron oxide nanoparticles, silver nanoparticles, gold nanoparticles, copper nanoparticles, graphite, graphene, graphene oxide, carbon black, carbon nanotubes, nitrogen carbide, transition metal carbides, and black phosphorus; When the stimulus response enhancement film is an electrical stimulus response enhancement film, the stimulus response matrix is ​​a composite of a polymer and a conductive filler; the stimulus response filler is one or more of graphite, carbon black, graphene, carbon nanotubes, acetylene black, silver nanoparticles, gold nanoparticles, copper nanoparticles, nickel powder, silver nanowires, gold nanowires, copper nanowires, metal oxide powders, conductive polymers, and transition metal carbides / nitrides; When the stimulus-responsive enhanced film is a moisture stimulus-responsive enhanced film, the stimulus-responsive matrix is ​​one or more of viscose, silk fibroin, cellulose, chitosan, sodium alginate, polyethylene oxide, polyvinyl alcohol, polyvinyl butyral, and polyvinyl pyrrolidone; the stimulus-responsive filler is one or more of metal organic frameworks, carbon-based materials, conductive polymers, transition metal carbides / nitrides, potassium titanate, polyacrylamide, and agar; When the stimulus response enhancement film is a magnetic field stimulus response enhancement film, the stimulus response matrix is ​​a composite of a polymer and a magnetic filler; the stimulus response filler is one or more of ferroferric oxide nanoparticles, iron oxide nanoparticles, ferrite particles, neodymium iron boron particles, iron powder, nickel powder, cobalt powder, and cobalt iron particles; The composite method of the stimulus-responsive matrix and the stimulus-responsive filler in composite molding is mixing; The molding method in the composite molding of the stimulus-responsive matrix and the stimulus-responsive filler is one or more of a casting method, a scraping method, a flow-casting method, a brushing method, and a vacuum filtration method.

5. A method for preparing a heat-pressed deformable fiber membrane according to any one of claims 1 to 4, comprising the following steps: (1) mixing an insulating polymer and a solvent, stirring, and obtaining a polymer solution; spinning the polymer solution to obtain a porous insulating polymer fiber membrane; (2) hot pressing the porous insulating polymer fiber membrane in a single-layer or multi-layer structure to obtain a micro-melted porous insulating polymer fiber membrane; (3) mixing a stimuli-responsive matrix, a stimuli-responsive filler and a solvent to obtain a mixed solution; and performing film-forming processing on the mixed solution to obtain a stimuli-responsive enhanced film; (4) The stimulus response enhanced membrane is sandwiched between the micro-melting porous insulating polymer fiber membranes, and the composite is formed by hot pressing to obtain a hot-pressed deformable fiber membrane with a sandwich structure.

6. The preparation method according to claim 5, characterized in that: The hot pressing process parameters in steps (2) and (4) are: hot pressing pressure 0.1-30 MPa, hot pressing temperature 50-250° C., and hot pressing time 0.1-60 min.

7. The preparation method according to claim 5, characterized in that: The mass ratio of the stimulus-responsive matrix to the stimulus-responsive filler in step (3) is 1:10 to 200:

1.

8. An application of the heat-pressed deformable fiber membrane according to any one of claims 1 to 4 in the fields of energy, information, medical treatment, and intelligent response, characterized in that: The applications in the energy field include energy collection or energy management equipment; the applications in the information field include sensing or information interaction equipment; the applications in the medical field include flexible or wearable medical devices; the applications in the intelligent response field include applications in artificial muscles, soft robots or human-computer interaction.

9. The use according to claim 8, characterized in that: One side of the heat-pressed deformable fiber membrane is compounded with an inert conductive adhesive tape, and a conductive layer is sputtered on the other side of the heat-pressed deformable fiber membrane using a gold spraying process to obtain a composite actuator with a sandwich structure.

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