Porous GNP / PDMS composite material, preparation method thereof and application of porous GNP / PDMS composite material in flexible sensor

Abstract

The invention discloses a porous GNP / PDMS composite material, a preparation method thereof and application of the porous GNP / PDMS composite material in a flexible sensor, and belongs to the technical field of flexible sensors and preparation of the flexible sensors. According to the preparation method, expanded polystyrene microspheres are taken as sacrificial templates to be combined with glucose, a spherical pore structure is constructed through a vacuum infiltration method, graphene is dispersed in a PDMS matrix by adopting a multi-step ultrasonic dispersion technology, and porous GNP / PDMS composite materials with different graphene contents are obtained. On the basis, a conductive electrode and a flexible packaging layer are combined to construct a high-sensitivity flexible sensor. Results show that the GNP / PDMS composite material containing 4 wt.% of graphene shows excellent mechanical properties, the elastic modulus is 2.43 MPa, the maximum tensile strength is 1.46 MPa, meanwhile, the recovery of more than 99.6% is maintained after 200 times of compression cycles, and the composite material shows very strong mechanical stability.

Description

Technical Field

[0001] This invention relates to a porous GNP / PDMS composite material, its preparation method, and its application in flexible sensors, belonging to the field of flexible sensor and its preparation technology. Background Technology

[0002] The rapid development of wearable electronics and soft robots has placed higher demands on the performance of flexible resistive sensors, including high sensitivity, mechanical compliance, and long-term stability. Porous polydimethylsiloxane (PDMS) composites, with their unique pore structure, good elasticity, and tunable mechanical properties, have become one of the most promising candidates for flexible sensing materials. However, existing pore fabrication methods have significant limitations. Traditional sacrificial template methods, using salt or glucose templates, are cost-effective and easy to remove, but they often result in irregular pore shapes, leading to localized stress concentrations that negatively impact the material's stability and durability. While gas foaming methods can produce spherical pores with more uniform stress distribution, precise control of the pore size is difficult, especially at small scales, limiting the material's performance consistency. Therefore, there is an urgent need for a pore fabrication strategy that can precisely control pore shape and size while significantly reducing stress concentration.

[0003] Graphene, with its excellent conductivity, is widely used in flexible sensing materials. Introducing graphene into porous PDMS can significantly improve conductivity, thereby enhancing sensing sensitivity, while addressing the inherent limitations of traditional porous structures, such as insufficient strength and stability. Traditional methods for preparing graphene / porous PDMS composites typically involve surface coating with a graphene layer; however, these coatings are susceptible to external environmental interference, leading to performance instability. Internal graphene filling reduces external interference but faces challenges in achieving sufficient conductivity at low graphene loadings, while high loadings often result in agglomeration, severely impacting mechanical and electrical stability. Furthermore, current graphene dispersion techniques, such as prolonged ultrasonication or surfactant-assisted methods, often fail to achieve uniform dispersion and optimal matrix compatibility. Crucially, most existing research focuses on optimizing either the pore structure or graphene content individually, neglecting the potential synergistic effect between these two factors. Therefore, an innovative manufacturing strategy for porous GNP / PDMS composites with well-controlled spherical pore structures is essential.

[0004] Contents This invention addresses the aforementioned problems of existing porous flexible composite materials by providing a porous GNP / PDMS composite material, its preparation method, and its application in flexible sensors.

[0005] The technical solution of the present invention: One objective of this invention is to provide a method for preparing porous GNP / PDMS composite materials, the method comprising the following steps: (1) Graphene was uniformly dispersed in ethyl acetate, and then the mixture was frozen to obtain a dispersion; (2) The dispersion is mixed with the base agent and curing agent of PDMS to obtain a GNP / PDMS mixture; (3) Dissolve glucose in ethanol / deionized water solution, stir evenly to obtain adhesive solution, continue to add EPS microspheres, stir, filter to remove solution, pour the mixture into mold, dry to obtain three-dimensional template structure; (4) Pour the GNP / PDMS mixture into the three-dimensional template structure, release the vacuum after vacuum treatment, so that the GNP / PDMS mixture fully fills the pores of the three-dimensional template structure, perform thermosetting treatment to obtain the composite material, immerse the composite material in tetrahydrofuran, and dissolve the EPS microspheres by ultrasonic treatment to obtain the porous GNP / PDMS composite material.

[0006] Further specifying, the mass percentage of graphene is 3-5 wt.% of the total mass of the PDMS binder and curing agent.

[0007] Further specified, the diameter of the EPS microspheres is 360 μm.

[0008] Further specified, the volume ratio of ethyl acetate to PDMS base agent is 2:1.

[0009] Further specified, in (1) the freezing temperature is -18°C and the time is 10 min.

[0010] Further specifying, the process of uniformly dispersing graphene in ethyl acetate in (1) is as follows: First, the mixture was stirred using a vortex mixer for 10 min; then, it was sonicated for 20 min using a low-power probe at 100% amplitude; finally, it was sonicated for 40 s using a high-power cell disruptor at 50% amplitude.

[0011] Further specifying, in (2), the process of mixing the dispersion with the PDMS base agent and curing agent is as follows: First, the mixture was mixed using an eddy current mixer for 2 minutes, and then ultrasonically treated for 5 minutes using a low-power probe at 100% amplitude.

[0012] Further specifying, in (2), the mass ratio of the base agent and the curing agent of PDMS is 10:1.

[0013] Further specifying, the ratio of glucose, ethanol and deionized water in (3) is 2 g: 3 mL: 3 mL.

[0014] Further specified, in (3) the drying temperature is 60℃ and the time is 2 h.

[0015] Further specified, in (4) the vacuum treatment pressure is -0.1 MPa and the time is 10 min.

[0016] Further, in (4), the ultrasonic treatment is performed in 3 cycles, each cycle lasting 30 min.

[0017] Further specifying, (4) the heat curing process is as follows: keep warm at 40℃ for 10 h, raise the temperature to 80℃ and keep warm for 3 h, and finally raise the temperature to 120℃ and keep warm for 3 h.

[0018] The second objective of this invention is to provide a porous GNP / PDMS composite material obtained by the above-mentioned preparation method.

[0019] The third objective of this invention is to provide an application of the above-mentioned porous GNP / PDMS composite material, specifically as a sensing layer for fabricating the conductive electrode layer of a flexible sensor.

[0020] The fourth objective of this invention is to provide a flexible sensor comprising the aforementioned porous GNP / PDMS composite material, a flexible PDMS thin film encapsulation layer, and a sensing layer composed of silver paste and copper foil.

[0021] The fifth objective of this invention is to provide a method for preparing the above-mentioned flexible sensor. The method involves sequentially combining a glass slide, a flexible PDMS film, an uncured PDMS liquid, a porous GNP / PDMS composite material, the flexible PDMS film, and the glass slide. The two ends of the porous GNP / PDMS composite material are connected to copper foil with silver paste. After hot pressing, the glass slide is removed to obtain the flexible sensor.

[0022] The sixth objective of this invention is to provide an application of the above-mentioned flexible sensor, specifically for the fabrication of flexible electronics, wearable sensors, and soft robots.

[0023] Beneficial effects: This invention uses expanded polystyrene microspheres (EPS microspheres) as a sacrificial template to bind glucose, constructing a spherical porous structure via vacuum infiltration. A multi-step ultrasonic dispersion technique is then employed to disperse graphene in a PDMS matrix, yielding porous GNP / PDMS composite materials with varying graphene contents. Based on this, a highly sensitive flexible sensor is constructed by combining conductive electrodes and a flexible encapsulation layer. Compared to existing technologies, this invention offers at least the following advantages: (1) In this invention, EPS microspheres are used as sacrificial templates to prepare porous composite materials with spherical pore structures by vacuum permeation. A multi-step ultrasonic dispersion method is used to improve the dispersion of GNP in the PDMS matrix and reduce the electroosmosis threshold to 2 wt.%. At the same time, glucose is used to enhance the adhesion between EPS microspheres by taking advantage of its cost-effectiveness and easy removal, thus ensuring the structural stability of the template in subsequent processing.

[0024] (2) This invention systematically studied the electrical conductivity, mechanical properties, and sensing sensitivity of the composite material. The results showed that the GNP / PDMS composite material containing 4 wt.% graphene exhibited excellent mechanical properties, with an elastic modulus of 2.43 MPa and a maximum tensile strength of 1.46 MPa. Furthermore, it maintained over 99.6% recovery after 200 compression cycles, demonstrating strong mechanical stability. The sensitivity of the GNP / PDMS composite material increased with increasing graphene content. The composite material containing 4 wt.% graphene showed the highest sensitivity at low strain (GF=65), while the composite material containing 3 wt.% graphene showed even higher sensitivity at high strain (GF=200). Therefore, the prepared porous GNP / PDMS composite material can be used to manufacture sensors with excellent strain sensing performance under tension, compression, and finger joint bending deformation, which is of great significance for the development of flexible electronics, wearable sensors, and soft robots. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation of porous GNP / PDMS composite materials according to the present invention; Figure 2 SEM images of the porous GNP / PDMS composite materials prepared in Example 1 and Comparative Example 1; Figure 3 SEM image of the porous GNP / PDMS composite material prepared in Comparative Example 2; Figure 4 SEM images and elemental distribution diagrams of the porous GNP / PDMS composite material prepared in Example 1; Figure 5 Stress distribution cloud diagrams of the porous GNP / PDMS composite material prepared in Example 1 under different tensile and compressive strains; Figure 6 A comparison of the stress-strain curves of the first and 200th compression cycles of the flexible sensor prepared in Example 1 under 10% strain conditions. Figure 7 Here are schematic diagrams and physical images of the flexible sensor prepared in Example 1; Figure 8 The resistance change response curve of the flexible sensor prepared in Example 1 under different tensile strains; Figure 9 The resistance change response curve of the flexible sensor prepared in Example 1 under 10% tensile strain; Figure 10 The resistance response curve of the flexible sensor prepared in Example 1 during repeated pressing cycles; Figure 11 The resistance response curve of the flexible sensor prepared in Example 1 during repeated bending of the finger joint; Figure 12 The resistivity response of the porous GNP / PDMS composite materials prepared in Example 1 and Comparative Examples 2-5 at 10% compressive strain; Figure 13 Stress-strain curves of porous GNP / PDMS composite materials prepared for Examples 1 and Comparative Examples 2-5 during compression. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0027] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art may make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0028] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0030] Example 1: like Figure 1 As shown, the process for preparing the porous GNP / PDMS composite material in this embodiment is as follows: Step (1): 40 mg of graphene was dispersed in 0.5 mL of ethyl acetate and initially mixed for 10 min using a vortex mixer; then, it was sonicated for 20 min using a low-power probe at 100% amplitude; finally, it was sonicated for 40 s using a high-power cell disruptor at 50% amplitude; the resulting mixture was cooled at -18°C for 10 min to obtain a dispersion. After cooling, the dispersion was mixed with 1 g of PDMS base agent and 0.1 g of PDMS curing agent, mixed using a vortex mixer for 2 min, and finally sonicated for 5 min using a low-power probe at 100% amplitude to obtain a GNP / PDMS mixture.

[0031] Step (2): Dissolve 2 g of glucose in a mixed solvent (3 mL of deionized water and 3 mL of ethanol) and stir magnetically for 30 min to obtain an adhesive solution. Immerse EPS microspheres with a diameter of 360 μm in the above glucose solution, filter out excess solution, pour the mixture into a mold, and dry at 60 °C for 2 h to obtain a three-dimensional template structure.

[0032] Step (3): The GNP / PDMS mixture was poured into a three-dimensional template structure and vacuum-permeated (-0.1 MPa) for 10 min to remove air bubbles and internal air from the EPS microsphere template. Then, the vacuum was released to allow the GNP / PDMS mixture to fully fill the pores of the EPS microsphere template. Thermosetting treatment was then performed: holding at 40℃ for 10 h, raising the temperature to 80℃ and holding for 3 h, and finally raising the temperature to 120℃ and holding for 3 h. The cured composite material was then immersed in tetrahydrofuran and ultrasonically treated for 3 cycles (30 min per cycle) to obtain a porous GNP / PDMS composite material, named A3.

[0033] The microstructure and elemental distribution of the porous GNP / PDMS composite material prepared in this embodiment were characterized, and the results are as follows: Figure 4 As shown in the figure, the carbon element distribution is relatively uniform, and no obvious agglomeration or high-density aggregation regions were observed, indicating that graphene is well dispersed in the PDMS matrix. Since the PDMS matrix itself contains methyl side chains in its organosilicon structure, a certain background intensity of carbon element signal can be observed in the energy dispersive spectroscopy (EDS) analysis. The EDS surface scan image reflects a relatively uniform overall carbon distribution, with no large-area, high-intensity carbon signal aggregation regions observed. This indicates that graphene has a good dispersion state in the PDMS matrix and is uniformly distributed on the inner surface and around the spherical cavities.

[0034] like Figure 7As shown, the flexible sensor prepared in this embodiment includes a porous GNP / PDMS composite material, a flexible PDMS film encapsulation layer, and a sensing layer composed of silver paste and copper foil. The porous graphene composite material layer is located in the center and has excellent compression response sensitivity. Its two ends are connected to copper foil electrodes through silver paste to form a complete signal acquisition path. The outermost layer is a flexible PDMS encapsulation film, which provides good mechanical protection and isolation from the external environment for the internal sensitive material.

[0035] The process for fabricating the flexible sensor in this embodiment is as follows: The glass slide, flexible PDMS film, uncured PDMS liquid, porous GNP / PDMS composite material, flexible PDMS film and glass slide are sequentially combined, and the two ends of the porous GNP / PDMS composite material are connected to copper foil with silver paste respectively. After hot pressing, the glass slide is removed to obtain a flexible sensor.

[0036] Example 2: The difference between this embodiment and Embodiment 1 is that the amount of graphene used is 35 mg, while the remaining process steps and parameter settings are the same as in Embodiment 1.

[0037] Example 3: The difference between this embodiment and Embodiment 1 is that the amount of graphene used is 45 mg, while the remaining process steps and parameter settings are the same as in Embodiment 1.

[0038] Comparative Example 1: The difference between this comparative example and Example 1 is that: low-power probe ultrasonic dispersion was not used, high-power cell disruptor ultrasonic dispersion was not used, and eddy current mixer was used for mixing for 30 min 40 s. The remaining process steps and parameter settings are the same as in Example 1.

[0039] The microstructure of the porous GNP / PDMS composite materials prepared in Example 1 and Comparative Example 1 was characterized, and the SEM images are shown below. Figure 2 As shown, (a) is Comparative Example 1, and (b) is Example 1. A comparison reveals that the cross-sectional view of the composite material sample prepared without high-power tip ultrasonic dispersion in Comparative Example 1 shows significant graphene agglomeration, while in Example 1, after high-power tip ultrasonic dispersion treatment, the graphene distribution within the PDMS matrix is ​​more uniform, the sheet structure is significantly expanded, and the agglomeration phenomenon is greatly reduced. This indicates that high-power tip ultrasonic dispersion effectively promotes further exfoliation of graphene sheets by enhancing cavitation and shear strength, while simultaneously inhibiting secondary agglomeration.

[0040] Comparative Example 2: The difference between this comparative example and Example 1 is that white sugar is used to replace the EPS microspheres in step (2). The remaining process steps and parameter settings are the same as in Example 1. The porous GNP / PDMS composite material prepared is named A1.

[0041] The microstructure of the porous GNP / PDMS composite material prepared in this comparative example was characterized, and the results are as follows: Figure 3 As shown in the figure, the porous GNP / PDMS composite material prepared using granulated sugar as a template forms a large-sized open pore structure inside, and the pore morphology basically retains the polyhedral characteristics of granulated sugar crystals. Comparative Example 3: The difference between this comparative example and Example 1 is that NaCl(a) is used instead of the EPS microspheres in step (2). The remaining process steps and parameter settings are the same as in Example 1. The resulting porous GNP / PDMS composite material is named A2. The NaCl(a) has a particle size of 470 μm and a angular polyhedral structure.

[0042] Comparative Example 4: The difference between this comparative example and Example 1 is that NaCl(b) is used instead of the EPS microspheres in step (2). The remaining process steps and parameter settings are the same as in Example 1. The resulting porous GNP / PDMS composite material is named A4. The NaCl(b) has a particle size of 352 μm and a rounded polyhedral structure.

[0043] Comparative Example 5: The difference between this comparative example and Example 1 is that granulated sugar is used to replace the EPS microspheres in step (2). The remaining process steps and parameter settings are the same as in Example 1. The resulting porous GNP / PDMS composite material is named A5.

[0044] Example of results: (1) Based on the finite element simulation results, the stress distribution cloud diagrams of the porous GNP / PDMS composite material prepared in Example 1 under different tensile and compressive strains are shown in the figure. Figure 5 The figure shows the stress distribution of the material under tensile stresses of 10%, 30%, and 100% and compressive stresses of 10%, 30%, and 50%, respectively. Figure 5The stress distribution at 0%, 30%, and 50% compressive strain shows that stress gradually concentrates in the region between adjacent spherical pores as strain increases. However, at the microscale, no significant stress concentration is observed directly at the pore boundaries, indicating that the spherical geometry effectively alleviates local stress accumulation. Comparing the stress-strain curves of the porous GNP / PDMS composite shows that the porous structure significantly reduces stress at the equivalent strain level. This reduction is attributed to the spherical pore design's ability to accommodate larger local deformations in the interpore region, thereby enhancing the material's strain sensitivity and electrical response. Furthermore, unlike traditional porous structures formed using glucose or salt particles (which typically introduce sharp corners leading to stress concentration), the smooth spherical pores used here contribute to a more uniform stress distribution. This provides theoretical support for optimizing the microstructure of composite materials to enhance sensing performance.

[0045] (2) Figure 6 The figure shows a comparison of the stress-strain curves of the first and 200th compression cycles of the flexible sensor prepared in Example 1 under 10% strain conditions. As can be seen from the figure, the stress-strain curves after 200 compressions are basically the same as those after the first compression, and the maximum stress deviation at 10% strain is less than 0.4%. This indicates that the porous GNP / PDMS composite material retains more than 99.6% recovery after 200 compression cycles, showing strong mechanical stability.

[0046] (3) Figure 8 The resistance-time response curves of the flexible sensor prepared in Example 1 under 60% and 100% strain conditions are shown in the figure. As can be seen from the figure, the resistance of the flexible sensor remains stable in the initial unstretched state, indicating that its internal graphene conductive network is in a stable connected state without external disturbance, exhibiting good electrical performance. When a tensile strain of 60% is applied, the sensor resistance increases significantly, showing a clear non-linear upward trend. This is mainly attributed to the increased spacing between graphene sheets and the reduced contact area, leading to interruption or migration of conductive paths, thereby increasing the overall resistance value. During the 60% strain holding stage, the resistance curve shows a slight decline, indicating that under constant stress, some graphene sheets undergo microscopic rearrangement or re-contact, and the conductive network partially recovers, resulting in a slight decrease in resistance. Further stretching the sensor to 100% causes the resistance value to continue to rise, and then shows a slight decline again during the holding stage, exhibiting a similar trend to the previous stage.

[0047] (4) Figure 9The flexible sensor prepared in Example 1 exhibits a resistance-time response curve under 10% strain after initial stretching cycles. As shown in the figure, the sensor resistance shows a periodic change during stretching, with a smooth overall curve, indicating that the material structure and conductive network have stabilized under strain. Each stretch-release process produces repeatable resistance fluctuations, with the amplitude between peaks and troughs remaining essentially constant. This demonstrates that after initial mechanical activation, the sensor structure possesses good recoverability and electrical response stability, and the conductive graphene network maintains strong reversible controllability under periodic strain.

[0048] (5) Figure 10 The figure shows the resistance of the flexible sensor prepared in Example 1 changing over time during multiple periodic external pressure cycles. As can be seen from the figure, the sensor resistance rises rapidly at the beginning of each pressure cycle, then slowly decreases as pressure continues to be applied. Once the external pressure is released, the sensor resistance immediately drops sharply, quickly approaching the initial baseline value, indicating strong structural resilience after stress removal. This rapid recovery behavior reflects the material's good elasticity and the ability to reconstruct its internal conductive structure, demonstrating the excellent dynamic response and reversibility of this composite material during periodic loading-unloading processes.

[0049] (6) Figure 11 The resistance-time response curves of the flexible sensor prepared in Example 1 during multiple natural finger bending-extension processes (the flexible sensor is located at the finger joint) are shown in the figure. As can be seen from the figure, each finger bending causes a significant change in the sensor resistance, exhibiting periodic fluctuation characteristics, indicating that the sensor has high sensitivity and responsiveness to dynamic deformation. Furthermore, the finger bending process involves not only local stretching but also combined bending and compressive strain within the material; that is, the upper surface of the sensor is subjected to tensile stress, while the lower surface is subjected to compressive strain. This non-uniform deformation leads to complex local adjustments in the graphene conductive network, resulting in minute perturbations in the resistance curve. The flexible sensor prepared in this invention can identify bending strain through the resistance change curve after the action ends, and the overall waveform of the curve is clear, indicating that the flexible sensor still possesses good signal recognition under nonlinear complex deformation conditions. The porous GNP / PDMS composite flexible sensor based on a spherical porous structure exhibits excellent strain response capabilities, can effectively distinguish different types of mechanical stimuli, and possesses excellent multifunctional sensing characteristics.

[0050] (7) The properties of the porous GNP / PDMS composites prepared in Examples 1 and Comparative Examples 2-5, the strain sensitivity coefficient at 10% strain, and the maximum stress at 10% compressive strain were characterized, and the results are as follows: Figure 12 and 13 And as shown in Table 1 below: Table 1

[0051] Depend on Figure 12 and Figure 13 As shown in Table 1 above, the porous GNP / PDMS composite material obtained in Example 1 using EPS microspheres as a pore-forming agent exhibits superior molding performance compared to porous materials prepared using other templates, resulting in uniformly distributed and clearly defined spherical pores. Graphene is also uniformly distributed within the matrix. All samples show significantly lower densities than non-porous composite materials, demonstrating a significant lightweight advantage. The porous GNP / PDMS composite material prepared using EPS microspheres as a template has a density of 0.31 g / cm³. 3 The porosity reaches 70.87%, the strain sensitivity coefficient at 10% strain is as high as 27, and the stress at 10% strain is 0.062 MPa. This indicates that the material has good compression recovery performance. After 200 cycles of compression performance testing, the maximum stress change of the material is less than 0.4%.

[0052] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a porous GNP / PDMS composite material, characterized in that, include: (1) Graphene was uniformly dispersed in ethyl acetate, and then the mixture was frozen to obtain a dispersion; (2) The dispersion is mixed with the base agent and curing agent of PDMS to obtain a GNP / PDMS mixture; (3) Dissolve glucose in ethanol / deionized water solution, stir evenly to obtain adhesive solution, continue to add EPS microspheres, stir, filter to remove solution, pour the mixture into mold, dry to obtain three-dimensional template structure; (4) Pour the GNP / PDMS mixture into the three-dimensional template structure, release the vacuum after vacuum treatment, so that the GNP / PDMS mixture fully fills the pores of the three-dimensional template structure, perform thermosetting treatment to obtain the composite material, immerse the composite material in tetrahydrofuran, and dissolve the EPS microspheres by ultrasonic treatment to obtain the porous GNP / PDMS composite material.

2. The preparation method according to claim 1, characterized in that, The mass percentage of graphene is 3-5 wt.% of the total mass of the PDMS binder and curing agent.

3. The preparation method according to claim 1, characterized in that, The volume ratio of ethyl acetate to PDMS base agent is 2:

1.

4. The preparation method according to claim 1, characterized in that, (1) The freezing temperature is -18°C and the time is 10 min.

5. The preparation method according to claim 1, characterized in that, (4) The heat curing process is as follows: keep warm at 40℃ for 10 h, raise the temperature to 80℃ and keep warm for 3 h, and finally raise the temperature to 120℃ and keep warm for 3 h.

6. A porous GNP / PDMS composite material obtained by the preparation method according to any one of claims 1 to 5.

7. The application of the porous GNP / PDMS composite material according to claim 6, characterized in that, The conductive electrode layer is used as a sensing layer in the fabrication of flexible sensors.

8. A flexible sensor, characterized in that, It includes the porous GNP / PDMS composite material as described in claim 6, the flexible PDMS thin film encapsulation layer, and the sensing layer composed of silver paste and copper foil.

9. A method for fabricating the flexible sensor according to claim 8, characterized in that, The glass slide, flexible PDMS film, uncured PDMS liquid, porous GNP / PDMS composite material, flexible PDMS film and glass slide are sequentially combined, and the two ends of the porous GNP / PDMS composite material are connected to copper foil with silver paste respectively. After hot pressing, the glass slide is removed to obtain a flexible sensor.

10. An application of the flexible sensor described in claim 8, characterized in that, Used in the fabrication of flexible electronics, wearable sensors, and soft robots.

Images