GCF / SGNS-SiO2 double-framework composite film and preparation method thereof

Abstract

The invention discloses a GCF / SGNS-SiO2 double-framework composite film and a preparation method thereof, and the method comprises the following steps: adding sulfonated graphene into a suspension of cross-linked collagenous fiber to prepare a cross-linked collagenous fiber composite sulfonated graphene suspension; carrying out directional freeze-drying treatment on the crosslinked collagen fiber composite sulfonated graphene suspension to prepare crosslinked collagen fiber composite sulfonated graphene aerogel; the preparation method comprises the following steps: adding silicon dioxide into a suspension of cross-linked collagenous fibers to prepare a cross-linked collagenous fiber composite silicon dioxide suspension, dipping cross-linked collagenous fiber composite sulfonated graphene aerogel into the cross-linked collagenous fiber composite silicon dioxide suspension, and then freeze-drying to prepare double-skeleton structure aerogel; and applying pressure to the double-skeleton structure aerogel to prepare the double-skeleton film. The method effectively improves the charge density of the flexible sensor through the synergistic effect of the vertical orientation inner skeleton and the inner and outer skeletons, reduces the interface transmission loss, and improves the stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of triboelectric flexible sensors and relates to a GCF / SGNS-SiO2 double-skeleton composite film and a preparation method thereof. Background Art

[0002] With the rapid development of flexible electronics and wearable technology, flexible sensors based on triboelectric nanogenerators (TENGs) are becoming a cutting-edge research hotspot. These sensors utilize the electrostatic induction effect generated when materials come into contact and separate to achieve energy conversion and signal acquisition. They offer unique advantages such as self-power, lightweight construction, a wide range of materials, and strong environmental adaptability. Their operating principle stems from the coupling of triboelectric charging and electrostatic induction: when two dissimilar materials come into contact, electron transfer at the interface generates a surface electrostatic charge. During separation, the charge imbalance creates a potential difference, driving the directional flow of electrons in the external circuit, thereby converting mechanical energy into an electrical signal output. This mechanism frees sensors from dependence on traditional batteries, significantly reducing system complexity and maintenance costs. Given these advantages, triboelectric flexible sensors exhibit significant application potential in health monitoring, human-computer interaction innovation, and sensory enhancements for soft robotics.

[0003] However, triboelectric flexible sensors still have many problems. First, they are limited by the upper limit of the surface charge density of the material (generally <250 μC / m 2 ), which makes the charge generation efficiency low; secondly, the interface impedance between the flexible substrate and the electrode causes signal attenuation, resulting in charge transfer loss; and environmental humidity and repeated deformation can easily cause charge leakage, resulting in poor charge storage stability, which seriously limits the practical application of triboelectric flexible sensors. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a GCF / SGNS-SiO2 dual-skeleton composite film and a preparation method thereof, thereby solving the technical problems of low charge density, high interface charge loss and poor stability of triboelectric flexible sensors in the prior art.

[0005] The present invention is achieved through the following technical solutions: A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film comprises the following steps: S1: cross-linking collagen fibers with glycerol to prepare a suspension of cross-linked collagen fibers, and then adding sulfonated graphene, stirring and blending to prepare a suspension of cross-linked collagen fibers and sulfonated graphene; S2: performing a directional freeze-drying process on the cross-linked collagen fiber composite sulfonated graphene suspension to prepare a cross-linked collagen fiber composite sulfonated graphene aerogel; S3: adding silica to the cross-linked collagen fiber suspension, stirring and blending to obtain a cross-linked collagen fiber composite silica suspension, impregnating the cross-linked collagen fiber composite sulfonated graphene aerogel into the cross-linked collagen fiber composite silica suspension, and then freeze-drying to obtain a double-skeleton aerogel; S4: applying pressure to the double-skeleton aerogel to obtain the double-skeleton film.

[0006] Preferably, the mass of the glycerol accounts for 35% of the mass of the collagen fibers.

[0007] Preferably, the mass ratio of the solid content of the sulfonated graphene to the cross-linked collagen fibers is (0.5-2):(6.7-1.8).

[0008] Preferably, the mass percentage of the silicon dioxide in the cross-linked collagen fibers is 0.5% to 3.0%.

[0009] Preferably, in step S1, the temperature for stirring and blending is 25-35°C; in step S3, the temperature for stirring and blending is 25-35°C.

[0010] Preferably, in step S2, the cross-linked collagen fiber composite sulfonated graphene suspension is subjected to a directional freeze-drying treatment, specifically: the cross-linked collagen fiber composite sulfonated graphene suspension is poured into a directional freezing mold, and then low-temperature frozen with liquid nitrogen for 0.5 to 1 hour, and then freeze-dried at -40 to -45°C for 3 to 5 days.

[0011] Preferably, in step S4, when pressure is applied to the double-skeleton aerogel, the pressure is 1-15 MPa and the time is 1-4 min.

[0012] A GCF / SGNS-SiO2 dual-skeleton composite film is prepared by the above method. The GCF / SGNS-SiO2 dual-skeleton composite film includes an inner skeleton and an outer skeleton. The inner skeleton contains sulfonated graphene and the outer skeleton contains silicon dioxide. The mass of the outer skeleton accounts for 0.2% to 1.0% of the total mass of the dual-skeleton film.

[0013] A tribopositive layer for a flexible sensor comprises the above-mentioned GCF / SGNS-SiO2 double-skeleton composite film.

[0014] A triboelectric flexible sensor comprises the above-mentioned flexible sensor tribopositive layer, wherein the open circuit voltage of the triboelectric flexible sensor is 300-325 V.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film. This method uses sulfonated graphene (SGNS) as an internal skeleton to construct a vertically oriented conductive network, providing high-speed charge transfer channels. Silicon dioxide (SiO2) serves as an external skeleton, acting as an electret material and capturing and storing charge through its high electron affinity. The dual-skeleton structure significantly increases the effective friction area. The molecular-level binding of SGNS to collagen fibers (ionic bonds between sulfonic acid groups and amino groups) enhances electron transfer efficiency, increases open-circuit voltage, and thus increases charge density. Furthermore, directional freeze-drying enables vertical ice crystal growth, forming ordered pores that reduce charge diffusion paths. Simultaneously, SGNS is embedded within the collagen fiber skeleton, forming a continuous conductive path, reducing electrode-substrate interface impedance and effectively reducing interfacial transmission losses. Furthermore, the external skeleton fills the internal skeleton pores, mechanically interlocking and distributing stress, inhibiting deformation-induced charge leakage. Glycerol crosslinking enhances film flexibility and maintains structural stability. In summary, this method, through the synergistic effects of the vertically oriented internal skeleton and the internal and external skeletons, effectively increases the charge density of the flexible sensor, reduces interfacial transmission losses, and enhances stability.

[0016] Furthermore, the mass of the glycerol accounts for 35% of the mass of the collagen fibers, which optimizes the cross-linking degree of the collagen fibers, imparts ultrahigh flexibility to the film, and inhibits charge leakage caused by humidity.

[0017] Furthermore, the mass ratio of the solid content of the sulfonated graphene to the cross-linked collagen fibers is (0.5-2):(6.7-1.8), which ensures that the inner skeleton forms a continuous conductive network while avoiding excessive clogging of the pores by SGNS.

[0018] Furthermore, the percentage of silicon dioxide in the cross-linked collagen fibers is 0.5% to 3.0%, which can endow the material with good charge storage capacity.

[0019] Furthermore, in step S1, the temperature for stirring and blending is 25-35°C; in step S3, the temperature for stirring and blending is 25-35°C, which can make the materials mixed evenly.

[0020] Furthermore, in step S2, the cross-linked collagen fiber composite sulfonated graphene suspension is subjected to a directional freeze-drying treatment, specifically: the cross-linked collagen fiber composite sulfonated graphene suspension is poured into a directional freezing mold, and then low-temperature frozen with liquid nitrogen for 0.5 to 1 hour, and then freeze-dried at -40 to -45°C for 3 to 5 days to successfully prepare an aerogel with a vertical pore structure.

[0021] Furthermore, in step S4, when pressure is applied to the double-skeleton aerogel, the pressure is 1-15 MPa and the time is 1-4 min, so that the double-skeleton aerogel is pressed into a double-skeleton film.

[0022] The present invention also discloses a GCF / SGNS-SiO2 double-skeleton composite film, which includes an inner skeleton and an outer skeleton. The inner skeleton contains sulfonated graphene, and the outer skeleton contains silicon dioxide. The mass of the outer skeleton accounts for 0.2% to 1.0% of the total mass of the double-skeleton film. This ratio can make the double-skeleton aerogel structure stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 Comparison results of the output performance of a double-skeleton film GCF / SGNS-SiO2 prepared in Examples 5 to 7 of the present invention and a silica composite collagen fiber film prepared in Comparative Example 2, where (a) is the open circuit voltage and (b) is the short circuit current; Figure 2 The SEM images (a) of the aerogel obtained by conventional freeze-drying technology in Comparative Example 1 and the SEM images of the aerogel obtained by vertical directional freeze-drying technology in Example 1 of the present invention are shown; Figure 3 (a) SEM photo and (b) EDS spectrum photo of the inner and outer double skeleton GCF / SGNS-SiO2 aerogel material prepared in Example 1 of the present invention; Figure 4 3D perspective view of the internal and external double skeleton GCF / SGNS-SiO2 aerogel material prepared by the present invention. DETAILED DESCRIPTION

[0025] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0027] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0028] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0029] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0030] The present invention discloses a method for preparing a double-skeleton film based on GCF / SGNS-SiO2, comprising the following steps: S1: Add the cross-linking agent glycerol (Gly) to the collagen fiber (GF) suspension, and mechanically stir the suspension in a constant temperature water bath to cross-link the collagen fibers with glycerol to prepare a cross-linked collagen fiber (GGF) suspension; disperse sulfonated graphene (SGNS) in the cross-linked collagen fiber suspension, and stir and blend at 25-35°C for 3-6 hours to prepare a sulfonated graphene composite cross-linked collagen fiber (GCF / SGNS) suspension; The mass of the glycerol accounts for 35% of the mass of the collagen fibers; Here, sulfonated graphene is used as an internal skeleton, and the mass ratio of the sulfonated graphene to the cross-linked collagen fiber solid content is (0.5-2):(6.7-1.8); S2: The GCF / SGNS suspension is subjected to a directional freeze-drying treatment to obtain a cross-linked collagen fiber composite sulfonated graphene (GCF / SGNS) aerogel. Specifically, the GCF / SGNS suspension is poured into a directional freezing mold, and then rapidly frozen by liquid nitrogen for 0.5 to 1 hour. The suspension is then transferred to a freeze dryer and freeze-dried at -40 to -45°C for 3 to 5 days to obtain the GCF / SGNS aerogel, which has a vertical pore structure. S3: dispersing silica in a suspension of cross-linked collagen fibers, stirring and blending at 25-35°C for 3-6 hours to obtain a cross-linked collagen fiber composite silica (GCF / SiO2) suspension; then filling it into the vertical pore structure of the GCF / SGNS aerogel by dipping. Specifically, the GCF / SGNS aerogel is immersed in the GCF / SiO2 suspension for 2-5 hours, then cryogenically frozen at 40°C for 3-6 hours, and then transferred to a freeze dryer at -40--45°C for freeze drying for 3-5 days to obtain a double-skeleton structure (GCF / SGNS-SiO2) aerogel; Here, silicon dioxide serves as an exoskeleton, and the mass percentage of silicon dioxide in the cross-linked collagen fibers is 0.5% to 3.0%.

[0031] S4: Applying pressure to the GCF / SGNS-SiO2 dual-skeleton aerogel at a pressure of 1-15 MPa for a period of 1-4 minutes to produce the GCF / SGNS-SiO2 dual-skeleton composite film. Preferably, the pressure is 5 MPa.

[0032] The present invention also discloses a GCF / SGNS-SiO2 dual-skeleton composite film produced by the above method. The GCF / SGNS-SiO2 dual-skeleton composite film comprises an internal skeleton and an external skeleton, wherein the internal skeleton comprises sulfonated graphene and the external skeleton comprises silicon dioxide. The mass of the external skeleton accounts for 0.2% to 1.0% of the total mass of the dual-skeleton film. The internal and external dual skeletons of the composite film were simulated and characterized using a K-Smith laser spectroscopy confocal microscope and a scanning electron microscope. The GCF / SGNS-SiO2 dual-skeleton composite film exhibits charge transport and storage functions.

[0033] In the present invention, an inner and outer double-skeleton film is constructed through a two-step process of directional freeze-drying and freeze-drying and a physical external pressure preparation process. This method enables the film to have a transmission skeleton with vertical pores and an energy storage skeleton filled in the pores, achieving efficient synergy between charge transfer and storage functions. When assembled into a device with a triboelectric negative layer, the synergistic effect of the double-skeleton structure not only significantly improves the triboelectric properties of the film, but also effectively disperses external mechanical stress through the close bonding and mutual support between the skeletons, giving the film excellent mechanical strength, thereby ensuring that the sensor has high output performance and good durability.

[0034] The present invention also discloses a tribopositive layer for a flexible sensor, comprising a GCF / SGNS-SiO2 dual-skeleton composite film of the present invention. Specifically, to prepare the tribopositive layer for a flexible sensor, the GCF / SGNS-SiO2 dual-skeleton composite film of the present invention is cut into desired dimensions, which may be (2-3) cm x (2-3) cm, preferably 3 cm x 3 cm.

[0035] The present invention also discloses a triboelectric flexible sensor comprising the aforementioned flexible sensor tribopositive layer and a tribonegative layer, preferably Ecoflex. After assembling the positive and negative layers, the triboelectric flexible sensor is constructed. The open-circuit voltage of the triboelectric flexible sensor is 300-325V. Ecoflex can be Ecoflex0030, which consists of silicone rubber, silicone oil, and additives, purchased from Smooth-On in the United States. Ecoflex0030 is divided into liquid A and liquid B. Upon use, liquid A and liquid B are blended in a 1:1 ratio by weight to form an Ecoflex mixed solution. The resulting mixture is rapidly stirred at room temperature and then coated using a 200 μm doctor blade. The resulting film is placed on a flat surface, dried at room temperature for 36 hours, and then cut into (1-3) cm x (1-3) cm pieces. When assembling the tribopositive and negative layers, foam paper is used to separate the ends to establish an initial separation distance. The cut size is preferably 3 cm x 3 cm.

[0036] The present invention discloses a method for preparing a GCF / SGNS-SiO2 double-skeleton composite film, which uses collagen fibers as a skeleton substrate, and is respectively added with sulfonated graphene and silica, and is prepared by directional freeze-drying, freeze-drying, and physical external pressure. This method does not require complex surface design, and can obtain a double-skeleton film with a rich vertical pore structure and filling and storage function. The sulfonated graphene composite collagen fiber aerogel of the inner skeleton provides an efficient transmission channel for the charge, and the silica composite collagen fiber filling material of the outer skeleton enhances the charge storage capacity, thereby synergistically improving the charge utilization efficiency and output performance of the film. At the same time, the molecular interaction between the collagen fibers and the composite material significantly improves the mechanical strength and flexibility of the film, ensuring the durability and adaptability of the device. The double-skeleton film is prepared into a positive layer and assembled with a negative layer, and the constructed triboelectric flexible sensor exhibits high output performance. The preparation process of the present invention is simple and environmentally friendly, the raw materials are widely available, it is suitable for large-scale production and promotion, and has broad application prospects.

[0037] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, 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 fall equally within the scope limited by the appended claims of the application.

[0038] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0039] Example 1 A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film comprises the following steps: (1) Weigh 50 g of cross-linked collagen fiber suspension into a beaker, add 0.3 g of sulfonated graphene and blend them. The mass of sulfonated graphene accounts for 35% of the mass of the cross-linked collagen fiber solid content. The blending temperature is 25°C and the blending time is 3 h. Stir evenly to obtain a GCF / SGNS suspension. Pour the GCF / SGNS suspension into a directional freezing mold and then freeze it rapidly with liquid nitrogen for 0.5 h. Then transfer it to a freeze dryer and freeze-dry it at -40°C for 3 days to obtain a GCF / SGNS aerogel.

[0040] (2) Weigh 50 g of the cross-linked collagen fiber suspension and add it into a beaker. Add 0.25 g of silica and blend it. The mass of silica accounts for 0.5% of the mass of the cross-linked collagen fiber. The blending temperature is 25 °C and the time is 5 h to obtain a GCF / SiO2 suspension. Immerse the GCF / SGNS aerogel in 30 g of the GCF / SiO2 suspension for 4 h to allow the GCF / SiO2 suspension to fill the pores of the GCF / SGNS aerogel. Then, freeze it at low temperature for 6 h and transfer it to a freeze dryer at -40 °C for freeze-drying for 5 days to obtain a GCF / SGNS-SiO2 aerogel.

[0041] (3) The GCF / SGNS-SiO2 aerogel was pressed into a film using a hydraulic press, with the pressure controlled at 5 MPa and the pressing time at 2 min. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectric material and assembled with the Ecoflex triboelectric layer to construct a triboelectric flexible sensor.

[0042] Figure 1 This is a comparison of the output performance of a triboelectric flexible sensor prepared in Example 1 of the present invention. As can be seen from the figure, the output performance of the inner and outer double-skeleton films of the charge transfer and storage layer as the tribopositive layer reaches a maximum of 328 V, while the ordinary freeze-drying method of adding electret silica is only 268 V. The output performance of the double skeleton is as high as 1.21 times that of the ordinary method.

[0043] Figure 2 The SEM photos of the pore structure of aerogels prepared by different freezing methods are (a) ordinary freeze drying method; (b) vertical freeze drying method. It can be seen from the figure that the growth direction of ice crystals in ordinary freeze drying aerogels is random, and the pores of aerogels formed after ice crystal sublimation are randomly distributed and disordered as a whole, and there are also certain differences in pore size. Figure 2 In the vertical directional freeze-drying shown in Figure (b), the ice crystals grow in a directional manner in the vertical direction, so the aerogel formed has an obvious vertical directional pore structure, which is orderly arranged in the vertical direction and has relatively uniform pore size.

[0044] Figure 3 (a) SEM photo and (b) EDS spectrum photo of the GCF / SGNS-SiO2 aerogel prepared in Example 1 of the present invention. Figure 3 The middle image (a) still shows the inner skeleton of the vertical pore structure, which contains a fine mesh structure and complex texture. Figure 3 (be) is the element distribution diagram of the material, showing the distribution of carbon (C), nitrogen (N), sulfur (S) and silicon (Si) elements respectively. Figure 3 (d) and Figure 3 Middle (e) shows the distribution of sulfur and silicon, respectively. The purple and blue areas show the local concentrations of S and Si elements. It can be seen that the S element is concentrated on the inner skeleton of the vertical pores, while the Si element is widely distributed in the vertical pores of the inner skeleton.

[0045] Figure 4 This is a 3D image of the GCF / SGNS-SiO2 aerogel prepared in Example 1 of the present invention. The inner and outer double skeleton structures of the charge transport and storage layers can be clearly seen.

[0046] Example 2 A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film comprises the following steps: (1) Weigh 50 g of cross-linked collagen fiber suspension into a beaker, add 0.2 g of sulfonated graphene and blend them. The mass of sulfonated graphene accounts for 25% of the mass of the cross-linked collagen fiber solid content. The blending temperature is 30°C and the blending time is 4 h. Stir evenly to obtain a GCF / SGN suspension. Pour the GCF / SGNS suspension into a directional freezing mold and then freeze it with liquid nitrogen for 0.5 h. Then transfer it to a freeze dryer and freeze-dry it at -40°C for 4 days to obtain a GCF / SGNS aerogel.

[0047] (2) Weigh 50 g of the cross-linked collagen fiber suspension and add it into a beaker. Add 0.5 g of silica and blend it. The mass of silica accounts for 1% of the mass of the cross-linked collagen fiber. The blending temperature is 35 °C and the time is 3 h to obtain a GCF / SiO2 suspension. Immerse the GCF / SGNS aerogel in 30 g of the GCF / SiO2 suspension for 2 to 5 h to allow the GCF / SiO2 suspension to fill the pores of the GCF / SGNS aerogel. Then, freeze it at low temperature for 3 h and then transfer it to a freeze dryer at -45 °C for lyophilization for 5 to obtain a GCF / SGNS-SiO2 aerogel.

[0048] (3) The GCF / SGNS-SiO2 aerogel was pressed into a film using a hydraulic press, with the pressure controlled at 1 MPa and the pressing time at 2 min. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectric material and assembled with the Ecoflex triboelectric layer to construct a self-morphological triboelectric flexible sensor.

[0049] Example 3 A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film comprises the following steps: (1) Weigh 50 g of cross-linked collagen fiber suspension into a beaker, add 0.4 g of sulfonated graphene and blend them. The mass of sulfonated graphene accounts for 45% of the mass of the cross-linked collagen fiber solid content. The blending temperature is 25°C and the blending time is 4 h. Stir evenly to obtain a GCF / SGN suspension. Pour the GCF / SGNS suspension into a directional freezing mold and then freeze it rapidly with liquid nitrogen for 0.5 h. Then transfer it to a freeze dryer and freeze-dry it at -40°C for 4 days to obtain a GCF / SGNS aerogel.

[0050] (2) Weigh 50 g of the cross-linked collagen fiber suspension and add it into a beaker. Add 1 g of silica and blend it. The mass of silica accounts for 2% of the mass of the cross-linked collagen fiber. The blending temperature is 25 °C and the time is 3 h to obtain a GCF / SiO2 suspension. Immerse the GCF / SGNS aerogel in 30 g of the GCF / SiO2 suspension for 2 to 5 h to allow the GCF / SiO2 suspension to fill the pores of the GCF / SGNS aerogel. Then, freeze it at low temperature for 3 to 6 h, and then transfer it to a freeze dryer at -40 °C and freeze-dry for 3 days to obtain a GCF / SGNS-SiO2 aerogel.

[0051] (3) The GCF / SGNS-SiO2 aerogel was pressed into a film using a hydraulic press, with the pressure controlled at 1 MPa and the pressing time at 2 min. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectric material and assembled with the Ecoflex triboelectric negative layer to construct a self-morphing triboelectric flexible sensor. The open circuit voltage of the triboelectric flexible sensor was 300 V.

[0052] Example 4 A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film comprises the following steps: (1) Weigh 50 g of cross-linked collagen fiber suspension into a beaker, add 0.4 g of sulfonated graphene and blend them. The mass of sulfonated graphene accounts for 45% of the mass of the cross-linked collagen fiber solid content. The blending temperature is 35°C and the blending time is 6 h. Stir evenly to obtain a GCF / SGN suspension. Pour the GCF / SGNS suspension into a directional freezing mold and freeze it rapidly with liquid nitrogen for 0.5 h. Then transfer it to a freeze dryer and freeze-dry it at -45°C for 5 days to obtain a GCF / SGNS aerogel.

[0053] (2) Weigh 50 g of the cross-linked collagen fiber suspension and add it into a beaker. Add 1 g of silica and blend it. The mass of silica accounts for 2% of the mass of the cross-linked collagen fiber. The blending temperature is 25 °C and the time is 3 h to obtain a GCF / SiO2 suspension. Immerse the GCF / SGNS aerogel in 30 g of the GCF / SiO2 suspension for 2 h to make the GCF / SiO2 suspension penetrate into the pores of the GCF / SGNS aerogel. Then, freeze it at low temperature for 6 h and then transfer it to a freeze dryer at -45 °C and freeze-dry for 3 days to obtain a GCF / SGNS-SiO2 aerogel.

[0054] (3) The GCF / SGNS-SiO2 aerogel was pressed into a film using a hydraulic press, with the pressure controlled at 10 MPa and the pressing time at 3 min. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectric material and assembled with the Ecoflex triboelectric negative layer to construct a self-morphing triboelectric flexible sensor. The open circuit voltage of the triboelectric flexible sensor was 325 V.

[0055] Example 5 A method for preparing a double-skeleton film based on GCF / SGNS-SiO2 comprises the following steps: S1: adding a cross-linking agent glycerol (Gly) to a collagen fiber (GF) suspension, and mechanically stirring the suspension in a constant temperature water bath to cross-link the collagen fibers with the glycerol, thereby preparing a cross-linked collagen fiber (GGF) suspension, wherein the mass of the glycerol accounts for 35% of the mass of the collagen fibers; Sulfonated graphene (SGNS) was dispersed in a suspension of cross-linked collagen fibers, with the sulfonated graphene serving as an internal skeleton. The mass ratio of the sulfonated graphene to the cross-linked collagen fibers was 35%. The mixture was stirred and blended at 25°C for 6 h to prepare a sulfonated graphene-composite cross-linked collagen fiber (GCF / SGNS) suspension. S2: The GCF / SGNS suspension is subjected to a directional freeze-drying treatment to obtain a cross-linked collagen fiber composite sulfonated graphene (GCF / SGNS) aerogel. Specifically, the GCF / SGNS suspension is poured into a directional freezing mold, and then rapidly frozen by liquid nitrogen for 0.5 h. The suspension is then transferred to a freeze dryer and freeze-dried at -40°C for 3 days to obtain the GCF / SGNS aerogel having a vertical pore structure. S3: Dispersing silica in a suspension of cross-linked collagen fibers, stirring and blending at 25°C for 6 h to prepare a cross-linked collagen fiber composite silica (GCF / SiO2) suspension, wherein silica serves as an exoskeleton, and the mass percentage of silica and cross-linked collagen fibers is 2%; the mass of the exoskeleton accounts for 0.83% of the total mass of the double-skeleton film; Then, it was filled into the vertical pore structure of the GCF / SGNS aerogel by dipping. Specifically, the GCF / SGNS aerogel was immersed in the GCF / SiO2 suspension for 2 hours, then cryogenically frozen at 40°C for 6 hours, and then transferred to a freeze dryer at -40°C for freeze drying for 5 days to obtain a double-skeleton structure (GCF / SGNS-SiO2) aerogel. S4: Pressure was applied to the GCF / SGNS-SiO2 dual-skeleton aerogel at 1 MPa for 1 minute to produce the GCF / SGNS-SiO2 dual-skeleton composite film. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectrically positive material and assembled with the Ecoflex triboelectrically negative layer to construct a self-morphing triboelectric flexible sensor. The open-circuit voltage of the triboelectric flexible sensor was 310 V.

[0056] Example 6 A method for preparing a double-skeleton film based on GCF / SGNS-SiO2 comprises the following steps: S1: adding a cross-linking agent glycerol (Gly) to a collagen fiber (GF) suspension, and mechanically stirring the suspension in a constant temperature water bath to cross-link the collagen fibers with the glycerol, thereby preparing a cross-linked collagen fiber (GGF) suspension, wherein the mass of the glycerol accounts for 35% of the mass of the collagen fibers; Sulfonated graphene (SGNS) was dispersed in a suspension of cross-linked collagen fibers, with the sulfonated graphene serving as an internal skeleton. The mass ratio of the sulfonated graphene to the cross-linked collagen fibers was 35%. The mixture was stirred and blended at 35°C for 3 h to prepare a sulfonated graphene-composite cross-linked collagen fiber (GCF / SGNS) suspension. S2: The GCF / SGNS suspension is subjected to a directional freeze-drying treatment to obtain a cross-linked collagen fiber composite sulfonated graphene (GCF / SGNS) aerogel. Specifically, the GCF / SGNS suspension is poured into a directional freezing mold, and then rapidly frozen by liquid nitrogen for 1 hour. The suspension is then transferred to a freeze dryer and freeze-dried at -45°C for 3 days to obtain the GCF / SGNS aerogel, which has a vertical pore structure. S3: dispersing silica in a suspension of cross-linked collagen fibers, stirring and blending at 35°C for 3 h to prepare a cross-linked collagen fiber composite silica (GCF / SiO2) suspension, wherein silica serves as an exoskeleton, the mass percentage of silica and cross-linked collagen fibers is 2%, and the mass of the exoskeleton accounts for 0.41% of the total mass of the double-skeleton film; Then, it was filled into the vertical pore structure of the GCF / SGNS aerogel by dipping. Specifically, the GCF / SGNS aerogel was immersed in the GCF / SiO2 suspension for 5 hours, then cryogenically frozen at 40°C for 6 hours, and then transferred to a freeze dryer at -45°C for freeze drying for 3 days to obtain a double-skeleton structure (GCF / SGNS-SiO2) aerogel. S4: Pressure was applied to the GCF / SGNS-SiO2 dual-skeleton aerogel at 15 MPa for 4 minutes to produce the GCF / SGNS-SiO2 dual-skeleton composite film. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectrically positive material and assembled with the Ecoflex triboelectrically negative layer to construct a self-morphing triboelectric flexible sensor. The open-circuit voltage of the triboelectric flexible sensor was 320 V.

[0057] Example 7 A method for preparing a double-skeleton film based on GCF / SGNS-SiO2 comprises the following steps: S1: adding a cross-linking agent glycerol (Gly) to a collagen fiber (GF) suspension, and mechanically stirring the suspension in a constant temperature water bath to cross-link the collagen fibers with the glycerol, thereby preparing a cross-linked collagen fiber (GGF) suspension, wherein the mass of the glycerol accounts for 35% of the mass of the collagen fibers; Sulfonated graphene (SGNS) was dispersed in a suspension of cross-linked collagen fibers, with the sulfonated graphene serving as an internal skeleton. The mass ratio of the sulfonated graphene to the cross-linked collagen fibers was 35%. The mixture was stirred and blended at 30°C for 4 hours to prepare a sulfonated graphene-composite cross-linked collagen fiber (GCF / SGNS) suspension. S2: The GCF / SGNS suspension is subjected to a directional freeze-drying treatment to obtain a cross-linked collagen fiber composite sulfonated graphene (GCF / SGNS) aerogel. Specifically, the GCF / SGNS suspension is poured into a directional freezing mold, and then rapidly frozen by liquid nitrogen for 0.8 h. The suspension is then transferred to a freeze dryer and freeze-dried at -45°C for 4 days to obtain the GCF / SGNS aerogel having a vertical pore structure. S3: dispersing silica in a suspension of cross-linked collagen fibers, stirring and blending at 30°C for 4 h to prepare a cross-linked collagen fiber composite silica (GCF / SiO2) suspension, wherein silica serves as an exoskeleton, the mass percentage of silica and cross-linked collagen fibers is 2%, and the mass of the exoskeleton accounts for 0.22% of the total mass of the double-skeleton film; Then, it was filled into the vertical pore structure of the GCF / SGNS aerogel by dipping. Specifically, the GCF / SGNS aerogel was immersed in the GCF / SiO2 suspension for 3 hours, then cryogenically frozen at 40°C for 4 hours, and then transferred to a freeze dryer at -40°C for freeze drying for 4 days to obtain a double-skeleton structure (GCF / SGNS-SiO2) aerogel. S4: Pressure was applied to the GCF / SGNS-SiO2 dual-skeleton aerogel at 10 MPa for 2 minutes to produce the GCF / SGNS-SiO2 dual-skeleton composite film. The pressed GCF / SGNS-SiO2 film was cut into 3 cm × 3 cm squares as a triboelectric material and assembled with the Ecoflex triboelectric negative layer to construct a self-morphing triboelectric flexible sensor. The open-circuit voltage of the triboelectric flexible sensor was 303 V. Comparative Example 1 The difference between this comparative example and Example 1 is that in step (1), the GCF / SGNS suspension is subjected to ordinary freeze-drying.

[0058] Comparative Example 2 The difference between this comparative example 2 and embodiment 5 is: A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film comprises the following steps: (1) Weigh 50 g of the cross-linked collagen fiber suspension into a beaker, add 0.4 g of sulfonated graphene, and blend the mixture. The mass of the sulfonated graphene accounts for 45% of the solid content of the cross-linked collagen fibers. The blending temperature is 35°C and the blending time is 6 h. Stir evenly to obtain a GCF / SGN suspension. (2) Adding silica to the GCF / SGN suspension so that the mass of silica accounts for 2% of the mass of the cross-linked collagen fibers, blending, freeze-drying, and applying pressure to obtain a silica composite collagen fiber film.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film, characterized in that: The following steps are involved: S1: cross-linking collagen fibers with glycerol to prepare a suspension of cross-linked collagen fibers, and then adding sulfonated graphene, stirring and blending to prepare a suspension of cross-linked collagen fibers and sulfonated graphene; S2: performing a directional freeze-drying process on the cross-linked collagen fiber composite sulfonated graphene suspension to prepare a cross-linked collagen fiber composite sulfonated graphene aerogel; S3: adding silica to the cross-linked collagen fiber suspension, stirring and blending to obtain a cross-linked collagen fiber composite silica suspension, impregnating the cross-linked collagen fiber composite sulfonated graphene aerogel into the cross-linked collagen fiber composite silica suspension, and then freeze-drying to obtain a double-skeleton aerogel; S4: applying pressure to the double-skeleton aerogel to obtain the double-skeleton film.

2. The method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film according to claim 1, characterized in that: The mass of the glycerol accounts for 35% of the mass of the collagen fibers.

3. The method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film according to claim 1, characterized in that: The mass ratio of the solid content of the sulfonated graphene to the cross-linked collagen fibers is (0.5-2):(6.7-1.8).

4. The method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film according to claim 1, characterized in that: The mass percentage of the silicon dioxide in the cross-linked collagen fibers is 0.5% to 3.0%.

5. The method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film according to claim 1, characterized in that: In step S1, the temperature for stirring and blending is 25-35°C; in step S3, the temperature for stirring and blending is 25-35°C.

6. The method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film according to claim 1, wherein: In step S2, the cross-linked collagen fiber composite sulfonated graphene suspension is subjected to a directional freeze-drying treatment, specifically: the cross-linked collagen fiber composite sulfonated graphene suspension is poured into a directional freezing mold, and then low-temperature frozen with liquid nitrogen for 0.5 to 1 hour, and then freeze-dried at -40 to -45°C for 3 to 5 days.

7. The method for preparing a GCF / SGNS-SiO2 dual-skeleton composite film according to claim 1, wherein: In step S4, when pressure is applied to the double-skeleton aerogel, the pressure is 1-15 MPa and the time is 1-4 min.

8. A GCF / SGNS-SiO2 double skeleton composite film, characterized in that: The GCF / SGNS-SiO2 dual-skeleton composite film is prepared by the method described in any one of claims 1 to 7, comprising an inner skeleton and an outer skeleton, wherein the inner skeleton comprises sulfonated graphene and the outer skeleton comprises silicon dioxide; the mass of the outer skeleton accounts for 0.2% to 1.0% of the total mass of the dual-skeleton film.

9. A tribopositive layer for a flexible sensor, characterized in that: It comprises a GCF / SGNS-SiO2 double-skeleton composite film as described in claim 8.

10. A triboelectric flexible sensor, characterized in that: A flexible sensor comprising a tribopositive layer as claimed in claim 9, wherein the open circuit voltage of the triboflexible sensor is 300-325 V.

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